Patent Application
20190288147
The field relates to dilute nitride optical absorber materials having graded doping profiles. The materials can be used in photodetectors and photovoltaic cells. Dilute nitride subcells having graded doping display improved efficiency, short circuit current density, and open circuit voltage.
The invention relates to compound semiconductor alloys comprising dilute nitride materials, and the use of the materials as optical absorbing layers for photodetectors, photovoltaic or solar cells and power converters, and in particular to dilute nitride materials wherein at least a portion of the dilute nitride material (such as a base region of a dilute nitride subcell in a photovoltaic cell) has a graded doping profile. Dilute nitride materials having graded doping profiles allow devices, such as photovoltaic cells, to exhibit improved quantum efficiencies across a broad range of irradiance energies.
III-V compound semiconductors materials are widely used in the fabrication of semiconductor optoelectronic devices such as light emitters, modulators, and detectors for a variety of applications. Devices capable of absorbing and detecting light may be used as photodetectors in communications systems, as power converters and as photovoltaic cells in tandem solar cells and multijunction solar cells. The bandgaps of the semiconductor materials used for such devices are chosen to (1) efficiently absorb the particular wavelength(s) of incident radiation relevant to a specific application and (2) convert that absorbed light into current, voltage, and/or energy as efficiently as possible. In the case of photodetectors for operation at telecommunications wavelengths, materials may be chosen to absorb efficiently at wavelengths between about 1.3 μm and 1.55 μm. A solar cell is a type of photodetector that is designed to efficiently absorb solar radiation.
Multijunction (MJ) solar cells may be formed using stacks of different semiconductor materials that have different bandgaps, selected to improve the absorption efficiency across the solar spectrum. Devices are typically fabricated on GaAs or Ge substrates. Selecting materials with the appropriate bandgaps, and in particular, material with a bandgap of approximately 1 eV, results in materials with different lattice constants needing to be integrated together, with metamorphic buffers being used to allow such integration. However, the use of metamorphic buffers requires thicker semiconductor layers, and can introduce defects, such as dislocations, into a material, based on lattice-mismatch between the different semiconductor materials. It is also very difficult to include more junctions within a device since additional bandgaps will occur for compositions of matter with yet further different lattice constants. Other factors equal, lattice-matched systems are preferable because they have proven reliability and require less semiconductor material than metamorphic solar cells.
Dilute nitrides are a class of III-V alloy materials (alloys having one or more elements from Group III on the periodic table along with one or more elements from Group V on the periodic table) with small fractions (e.g., <5 atomic percent) of nitrogen. These alloys are of particular interest for applications including telecommunications, power conversion and solar cells, since their bandgaps can be tuned between about 0.7 eV and 1.3 eV, while being lattice-matched or pseudomorphically strained to an underlying substrate such as GaAs or Ge. This makes it possible to integrate a lattice-matched dilute nitride material with an approximately 1 eV bandgap into a multi junction solar cell with substantial efficiency improvements.
GaInNAs, GaNAsSb and GaInNAsSb are some of the dilute nitride materials that have been studied as potentially useful for multi junction solar cells (see, e.g., A. J. Ptak et al., Journal of Applied Physics 98 (2005) 094501 and Yoon et al., Photovoltaic Specialists Conference (PVSC), 2009 34th IEEE, pp 76-80, 7-12, Jun. 2009; doi: 10.1109/PVSC.2009.5411736). Furthermore, the use of four-junction GaInP/GaAs/dilute-nitride/Ge solar cell structure holds the promise of efficiencies exceeding those of the standard metamorphic and lattice matched three junction cell, which at present are the benchmark for high-efficiency multi junction cell performance. (Friedman et al., Progress in Photovoltaics: Research and Applications 10 (2002), 331). To make that promise a reality, what is needed is a material that is lattice matched to GaAs and Ge with a band gap of near 1 eV and that produces open circuit voltage greater than 0.3 V with sufficient current to match the (Al)InGaP and (In)GaAs sub-cells in a multi-junction solar cell. It should be noted that a multi junction solar cell for terrestrial use is integrated into a concentrated photovoltaic system. Such a system employs concentrating optics consisting of dish reflectors or Fresnel lenses that concentrate sunlight onto the solar cell. It is possible that a concentrator's optics may attenuate light in a particular wavelength region which may be detrimental to the dilute nitride sub-cell. It is therefore of utmost importance that higher current be generated in the dilute nitride sub-cell so any loss due to the concentrator optics does not inhibit the performance of the multi junction solar cell.
In a multi junction solar cell, each of the sub-cells is attached in series to other sub-cells, typically using tunnel junction diodes to connect the individual sub-cells to one another. Since the total current generated by the full stack of sub-cells must pass through all the sub-cells, the sub-cell passing the least amount of current will be the current-limiting cell for the entire stack, and by the same virtue, the efficiency-limiting cell. It is therefore of greatest importance that each sub-cell be current matched to the other sub-cells in the stack for best efficiency. This is particularly important if dilute nitride sub-cells are to be used because dilute nitride semiconductor materials historically have been plagued with poor minority carrier transport properties that prove detrimental when incorporated into a larger solar cell.
Although dilute nitride alloys have other properties that make them desirable for use in multi-junction structures, particularly the flexibility with which their bandgaps and lattice constants can be fine-tuned as part of their design, the minority carrier lifetime and diffusion lengths for these sub-cells are typically worse than with conventional solar cell semiconductors such as GaAs and InGaP used in conventional multi junction solar cells, thus resulting in a loss of short circuit current, open circuit voltage or both. Moreover, the interface between the back-surface field and the base of the dilute nitride sub-cell may have high surface recombination velocity, which could further reduce the short circuit current and open circuit voltage of the sub-cell. As a result of these problems, photocurrents generated in dilute nitride sub-cells are typically lower than with more traditional materials. (D. B. Jackrel et al., Journal of Applied Physics 101 (114916) 2007).
Dopant variation in solar cells is generally known. See M. A. Green, Progress in Photovoltaics: Research and Applications 17 (2009). U.S. Pat. No. 7,727,795 is an example of a solar cell design using exponential doping in parts of a solar cell structure, evidently for multi junction solar cells grown in an inverted metamorphic and lattice mismatched structure. However, the application to dilute nitride sub-cells is not suggested and is not obvious, due to the anomalous characteristics of dilute nitrides. Dilute nitrides are a novel class of materials, which frequently exhibit different behavior than seen in traditional semiconductor alloys. For example, bandgap bowing as a function of alloy composition is very different in dilute nitrides as compared to traditional semiconductors (e.g., Wu et al., Semiconductor Science and Technology 17, 860 (2002)). Likewise, the standard dopants and doping profiles used for traditional semiconductors such as GaAs and InGaP do not result in comparable characteristics in dilute nitride semiconductors. For example, dopant incorporation in dilute nitrides has anomalous behavior. A Yu et al. paper reported that when dilute nitride thin films are doped heavily with Si, the Si and N mutually passivate each other's electronic activity (Yu et. al. App. Phys. Lett. 83, 2844 (2003)). Similarly, Janotti et. al. (Phys. Rev. Lett. 100, 045505 (2008)) suggested that while the physics of n-type and p-type doping in the parent compounds GaAs and GaN is well established, doping in GaAs1-xNx is much less explored and the interaction between extrinsic dopants and N in GaAs1-xNx alloys can lead to entirely new phenomena. They also pointed that rapid thermal annealing of Si-doped dilute (In)GaAsN alloys at temperatures above 800° C. leads to a drastic increase in the electrical resistivity. Due to the uncertainties associated with doping profiles and outcomes, and due to the unique properties of dilute nitrides, it is not apparent to one of ordinary skill how the concepts taught therein could be incorporated into a solar cell employing dilute nitride elements having portions subjected to controlled doping. Moreover, due to difficulties in doping the dilute nitride alloys, the literature teaches that dilute nitride alloys should not be doped (i.e., should be intrinsic) when incorporated into solar cell structures, for enhancement of the current collection (e.g., Ptak et al., J. Appl. Phys. 98, 094501 (2005); Volz et al., J. Crys. Growth 310, 2222 (2008)), and for increasing the minority carrier lifetime (Tukiainen et al., J. Green Eng. 5, 113-132 (2016). Rather, the literature teaches that the use of doping in the base of the dilute nitride solar cell leads to decreased performance.
Known as well, as previously discussed, dilute nitride cells were thought to have significant drawbacks such that their incorporation into multi junction solar cells would have led to substantial loss in the efficiency of such a solar cell, thus making dilute nitride cells less attractive commercially than other types of materials. It is desirable to improve current collection in dilute nitride based sub-cells without an accompanying loss of short circuit current, open circuit voltage or both.
According to the invention, a lattice-matched optoelectronic device, such as a photodetector or a solar cell, with a dilute nitride-based optically absorbing layer, such as a base region of a solar cell, has a graded doping profile in all or part of the dilute nitride layer, a graded doping profile being defined as a doping profile wherein the concentration of dopant increases or decreases from the top to bottom of the layer or within a portion of the layer, where top and bottom are defined relative to the orientation of the optoelectronic device in operation, the top being closest to the radiation source.
The dilute nitride base or optical absorber layer can have a bandgap within the range of 0.7 eV to 1.3 eV, or from 0.9 eV to 1.25 eV. A dilute nitride base or optical absorber layer can comprise a GaInNAsSb, GaInNAsBi, GaInNAsSbBi, GaNAsSb, GaNAsBi or GaNAsSbBi alloy, and can comprise an n-type dopant or a p-type dopant.
The optoelectronic device can be a solar cell with at least one dilute nitride based sub-cell. The dilute nitride based subcell includes an emitter layer with a larger bandgap than that of the dilute nitride region that faces incoming light, a dilute nitride base region underlying the emitter layer having a bandgap less than that of the emitter, followed by a back surface field, that has a larger bandgap than the dilute nitride region, overlying a substrate. Each of the emitter, base, and back surface field can be lattice-matched to a substrate such as a GaAs or Ge substrate. A Ge substrate can include a (Si,Sn)Ge material. A dilute nitride base can have a doping profile in which the dopant concentration at the dilute nitride base-back surface field interface is higher than the dopant concentration at the emitter-dilute nitride base interface. The doped dilute nitride subcells exhibit improved properties compared to undoped or intrinsically doped dilute nitride subcells.
An (In)GaAs emitter can overlie a dilute nitride base, the dilute nitride base can overlie a (In)GaAs back surface field, and a (In)GaAs back surface field can overlie a p-type GaAs or p-type Ge substrate. The (In)GaAs emitter can be doped with an n-type dopant such as Si, Te, or Se, or a combination of any of the foregoing. The dilute nitride base can include a first base portion and a second base portion. The first base portion can extend from the interface between the dilute nitride base and the (In)GaAs emitter to the interface between the first base portion and the second base portion. The first base portion can be intrinsically doped. The second base portion can comprise a dopant concentration that increases exponentially or linearly from the interface between the second base portion and the first base portion to the interface between the second base portion and the (In)GaAs back surface field. The second base portion can comprise a p-type dopant such as Be, C, Zn, or a combination of any of the foregoing.
In another embodiment of the invention, an (In)GaAs emitter overlies a dilute nitride base, which overlies an (In)GaAs back surface field on an n-type GaAs or Ge substrate. The (In)GaAs emitter can be doped with Be, C, Zn, or a combination of any of the foregoing. The dilute nitride base comprises a first base portion and a second base portion. The first base portion extends from its interface with the (In)GaAs emitter to its interface with the second base portion and can be intrinsically doped. The second base portion comprises a dopant concentration that increases exponentially or linearly from its interface with the first base portion to its interface with the (In)GaAs back surface field. The dopant in the second base portion can comprise Si, Te, Se, or a combination of any of the foregoing.
In another embodiment of the invention, an (In)GaAs emitter overlies a dilute nitride base, which overlies an (In)GaAs back surface field on an n-type GaAs or an n-type Ge substrate. The (In)GaAs emitter is doped with Be, C, Zn, or a combination of any of the foregoing. The dilute nitride base is characterized by an increase in dopant concentration from its interface with the (In)GaAs emitter to its interface with the (In)GaAs back surface field. The dopant in the dilute nitride base can comprise Si, Te, or Se, or a combination of any of the foregoing. The dilute nitride base can be characterized by a doping profile that is linear or exponential, and the (In)GaAs emitter can be characterized by a doping profile that is constant.
In another embodiment of the invention, an (In)GaAs emitter overlies a dilute nitride base, which overlies an (In)GaAs back surface field on a p-type GaAs or a p-type Ge substrate. The (In)GaAs emitter can be doped with Si, Te, Se, or a combination of any of the foregoing. The dilute nitride base is characterized by an increase in dopant concentration from its interface with the (In)GaAs emitter to its interface with the (In)GaAs back surface field. The dopant in the dilute nitride base can comprise Be, C, Zn, or a combination of any of the foregoing. The dilute nitride base and the (In)GaAs emitter can be characterized by a doping profile that is linear or exponential, and the (In)GaAs emitter can be characterized by a doping profile that is constant.
A lattice matched multi junction solar cell can have an upper sub-cell, a middle sub-cell and a lower dilute nitride sub-cell, the lower dilute nitride sub-cell having graded doping in the base and/or the emitter so as to improve its solar cell performance characteristics. In construction, the dilute nitride sub-cell may have the lowest bandgap and be lattice matched to a substrate; the middle sub-cell typically has a higher bandgap than the dilute nitride sub-cell and is lattice matched to the dilute nitride sub-cell. The upper sub-cell typically has the highest bandgap and is lattice matched to the adjacent sub-cell. In further embodiments, a multi junction solar cell according to the invention may comprise four, five or more sub-cells in which the one or more sub-cells may each contain dilute nitride alloys with a graded doping profile.
An optoelectronic device can be a photodetector with a dilute nitride optical absorber layer having a graded doping profile. The dilute nitride optical absorber can be situated between a first layer of a higher bandgap material having a first doping type and a second layer of a higher bandgap material having a second doping type, opposite to the first doping type that forms a p-i-n (or n-i-p) structure.
In one embodiment, the device is a photodetector and the doping profile for the dilute nitride layer is chosen to have two sub-regions, wherein no doping or uniform doping is used for the sub-region closer to the overlying wider-bandgap layer and graded doping is used in the other sub-region.
Common to all of these embodiments is a significant functional relationship between overall performance and the vertical distribution of doping in the base and/or emitter of the dilute nitride sub-cells, or the dilute nitride absorber layer of a photodetector. The doping concentration may be selected to have positional dependence, in which dependence varies as a function of vertical position in the base or the emitter. By way of an example, the doping could be designed to increase linearly or exponentially from the top to bottom in the base. Stated in mathematical terms, the doping concentration “d” has a functional dependence such that d−F(x) (i.e., doping is a function of position) where the x is the vertical position in the base and or emitter such that x is zero at the emitter/base junction and increases with distance from this junction. The manner and distribution of the doping (i.e., the function F) is selected to improve and ultimately to optimize the short circuit current and the open circuit voltage that would otherwise exist in the dilute nitride layer. The invention thus provides a lattice matched multi junction solar cell containing one or more dilute nitride sub-cells and having enhanced efficiency compared to that of a multi junction solar cell without such distribution of doping.
In one embodiment of the invention, the device is a solar cell and the doping profile for the dilute nitride layer is changed in the base of the solar cell such that it is the least at the emitter base junction and increases away from it. The precise distribution function for the increase is chosen to gain maximum current and voltage enhancement for the dilute nitride sub-cell.
In another embodiment, the device is a solar cell and the doping profile for the dilute nitride layer is chosen to have two sub-regions in the base, wherein no doping or uniform doping is used for the sub-region closer to the emitter-base junction and graded doping is used in the other sub-region.
The invention will be better understood by reference to the following detailed description in connection with the accompanying drawings.
Dilute nitride semiconductor materials are advantageous as photovoltaic cell materials because the lattice constant can be varied substantially to match a broad range of substrates and/or subcells formed from semiconductor materials other than dilute nitrides. Dilute nitrides are also advantageous for photodetectors formed on GaAs substrates, allowing the optical absorption at extended wavelengths up to about 1.6 μm that are typically absorbed using InGaAs materials formed on (more fragile and more expensive) InP substrates. Examples of dilute nitrides include GaInNAsSb, GaInNAsBi, GaInNAsSbBi, GaNAsSb, GaNAsBi and GaNAsSbBi. The lattice constant and band gap of a dilute nitride can be controlled by the relative fractions of the different group IIIA and group VA elements. Thus, by tailoring the compositions (i.e., the elements and quantities) of a dilute nitride material, a wide range of lattice constants and band gaps may be obtained. Further, high quality material may be obtained by optimizing the composition around a specific lattice constant and band gap, while limiting the total Sb and/or Bi content, for example, to no more than 20 percent of the Group V lattice sites, such as no more than 10 percent of the Group V lattice sites. Sb and Bi are believed to act as surfactants that promote smooth growth morphology of the III-AsNV dilute nitride alloys. In addition, Sb and Bi can facilitate uniform incorporation of N and minimize the formation of nitrogen-related defects. The incorporation of Sb and Bi can enhance the overall nitrogen incorporation and reduce the alloy band gap. However, there are additional defects created by Sb and Bi and therefore it is desirable that the total concentration of Sb and/or Bi should be limited to no more than 20 percent of the Group V lattice sites. Further, the limit to the Sb and Bi content decreases with decreasing nitrogen content. Alloys that include In can have even lower limits to the total content because In can reduce the amount of Sb needed to tailor the lattice constant. For alloys that include In, the total Sb and/or Bi content may be limited to no more than 5 percent of the Group V lattice sites, in certain embodiments, to no more than 1.5 percent of the Group V lattice sites, and in certain embodiments, to no more than 0.2 percent of the Group V lattice sites. For example, Ga1-xInxNyAs1-y-zSbz, disclosed in U.S. Application Publication No. 2010/0319764, can produce a high-quality material when substantially lattice-matched to a GaAs or a Ge substrate in the composition range of 0.08≤x≤0.18, 0.025≤y≤0.04 and 0.001≤z≤0.03, with a band gap of at least 0.9 eV such as from 0.9 eV to 1.25 eV.
In certain embodiments of dilute nitrides provided by the present disclosure, the N composition is not more than 5.5 percent of the Group V lattice sites. In certain embodiments the N composition is not more than 4 percent, and in certain embodiments, not more than 3.5 percent.
Embodiments of the present disclosure include dilute nitride optical absorption layers, comprising GaInNAsSb, GaInNAsBi, or GaInNAsBiSb that are included in photodetectors or in the base layer of a dilute nitride subcell that can be incorporated into multijunction photovoltaic cells that perform at high efficiencies. The band gaps of the dilute nitrides can be tailored by varying the composition while controlling the overall content of Sb and/or Bi. Thus, a dilute nitride subcell with a band gap suitable for integrating with other subcells may be fabricated while maintaining substantial lattice-matching to each of the other subcells and to the substrate. The band gaps and compositions can be tailored so that the short-circuit current density produced by the dilute nitride subcells will be the same as or slightly greater than the short-circuit current density of each of the other subcells in the photovoltaic cell. Because dilute nitrides provide high quality, lattice-matched and band gap-tunable subcells, photovoltaic cells comprising dilute nitride subcells can achieve high conversion efficiencies. The increase in efficiency is largely due to less light energy being lost as heat, as the additional subcells allow more of the incident photons to be absorbed by semiconductor materials with band gaps closer to the energy of the incident photons. In addition, there will be lower series resistance losses in these multijunction photovoltaic cells compared to other photovoltaic cells due to the lower operating currents. At higher concentrations of sunlight, the reduced series resistance losses become more pronounced. Depending on the band gap of the bottom subcell, the collection of a wider range of photons in the solar spectrum may also contribute to the increased efficiency.
In some embodiments, the GaInNAsSb optical absorption layer, such as the base of a photovoltaic cell, can comprise Ga1-xInxNyAs1-y-zSbz having values for x, y, and z of 0.03≤x≤0.19, 0.008≤y≤0.055, and 0.001≤z≤0.05, and a band gap within the range from 0.9 to 1.25 eV. In some embodiments, a GaInNAsSb optical absorption layer can have a composition of Ga1-xInxNyAs1-y-zSbz having values for x, y, and z of 0.06≤x≤0.09, 0.01≤y≤0.03, and 0.003≤z≤0.02, and can have a band gap within the range from 1 eV to 1.16 eV. In some embodiments, a GaInNAsSb optical absorption layer can have a composition of Ga1-xInxNyAs1-y-zSbz having values for x, y, and z of 0.12≤x≤0.14, 0.025≤y≤0.035, and 0.005≤z≤0.015, and can have a band gap of around 0.96 eV. In some embodiments, a GaInNAsSb optical absorption layer for the base layer of a subcell of a photovoltaic cell can have a composition of Ga1-xInxNyAs1-y-zSbz having values for x, y, and z of 0.11≤x≤0.15, 0.025≤y≤0.04, and 0.003≤z≤0.015, and can have a band gap within the range from 0.95 eV to 0.98 eV. In some embodiments, a GaInNAsSb subcell can be characterized by an Eg/q-Voc equal to or greater than 0.55 V measured using a 1 sun AM1.5D spectrum at a junction temperature of 25° C. In some embodiments, a GaInNAsSb subcell can be characterized by an Eg/q-Voc from 0.4 V to 0.7 V measured using a 1 sun AM1.5D spectrum at a junction temperature of 25° C. The Ga1-xInxNyAs1-y-zSbz subcells characterized by the alloy compositions and band gaps disclosed in this paragraph can exhibit the efficiencies presented in
In some embodiments, a GaInNAsBi optical absorption layer can comprise Ga1-xInxNyAs1-y-zBiz having values for x, y, and z of 0.03≤x≤0.19, 0.008≤y≤0.055, and 0.001≤z≤0.015, and can have a band gap within a range from 0.9 to 1.25 eV. In some embodiments, a GaInNAsBi optical absorption layer can comprise Ga1-xInxNyAs1-y-zBiz having values for x, y and z of 0.06≤x≤0.09, 0.01≤y≤0.03, and 0.001≤z≤0.002, and can have a band gap within a range from 1 eV to 1.16 eV. In some embodiments, a GaInNAsBi optical absorption layer can comprise of Ga1-xInxNyAs1-y-zBiz having values for x, y and z of 0.12≤x≤0.14, 0.025≤y≤0.035, and 0.001≤z≤0.005, and can have a band gap of about 0.96 eV. In some embodiments, a GaInNAsBi optical absorption layer can comprise Ga1-xInxNyAs1-y-zBiz having values for x, y and z of 0.11≤x≤0.15, 0.025≤y≤0.04, and 0.001≤z≤0.005, and can have a band gap within a range from 0.95 eV to 0.98 eV. In some embodiments, a GaInNAsSbBi optical absorption layer can comprise Ga1-xInxNyAs1-y-z1-z2Sbz1Biz2 having values for x, y, z1, and z2 of 0.03≤x≤0.19, 0.008≤y≤0.055, and 0.001≤z1+z2≤0.05, and can have a band gap within a range from 0.9 to 1.25 eV. In some embodiments, a GaInNAsSbBi optical absorption layer can comprise Ga1-xInxNyAs1-y-zSbz1Biz2 having values for x, y, z1, and z2 of 0.06≤x≤0.09, 0.01≤y≤0.03, and 0.001≤z1+z2≤0.02; and can have a band gap within a range from 1 eV to 1.16 eV. In some embodiments, a GaInNAsSbBi optical absorption layer can comprise Ga1-xInxNyAs1-y-zSbz1Biz2 having values for x, y, z1, and z2 of 0.12≤x≤0.14, 0.025≤y≤0.035, and 0.001≤z1+z2≤0.015, and can have a band gap of about 0.96 eV. In some embodiments, a GaInNAsSbBi optical absorption layer can comprise Ga1-xInxNyAs1-y-z1-z2Sbz1Biz2 having values for x, y, z1, and z2 of 0.11≤x≤0.15, 0.025≤y≤0.04, and 0.001≤z1+z2 ≤0.015, and can have a band gap within a range from 0.95 eV to 0.98 eV.
Dilute nitride subcells provided by the present disclosure can be fabricated to provide a high efficiency. A high efficiency represents an efficiency greater than 70%, greater than 80%, or greater than 90% over at least a portion of incident photon energies between 0.95 eV and 1.38 eV (wavelengths from 1300 nm to 900 nm) depending on the band gap of the dilute nitride solar cell. Factors that contribute to providing high efficiency dilute nitride subcells include, for example, the band gaps of the individual subcells, which in turn depends on the semiconductor composition of the subcells, doping levels and doping profiles, thicknesses of the subcells, quality of lattice matching, defect densities, growth conditions, annealing temperatures and profiles, impurity levels, and the semiconductor alloy electronic properties such as recombination velocity, diffusion length, lifetime, and others.
Embodiments of the present invention includes dilute nitride subcells that are doped with elemental impurities and designed for incorporation into multijunction photovoltaic cells. In certain embodiments provided by the present disclosure, the semiconductor layers can be fabricated using molecular beam epitaxy (MBE) and/or chemical vapor deposition (CVD). Certain embodiments of the invention display improved performance characteristics due to specific doping/impurity profiles, i.e. the tailored vertical distribution of one or more elemental dopants/impurities, within the dilute nitride base and/or the emitter of the subcell. Due to interactions between the different elements, as well as factors such as the strain in the layer, the relationship between composition and band gap for dilute nitrides is not a simple function of composition. As the composition is varied within the dilute nitride material system, the growth conditions need to be modified. For example, for (Al,In)GaAs, the growth temperature will increase as the fraction of Al increases and decrease as the fraction of In increases, in order to maintain the same material quality. Thus, as a composition of either the dilute nitride material or the other subcells of the multijunction photovoltaic cell is changed, the growth temperature as well as other growth conditions must be adjusted accordingly. The thermal dose applied to dilute nitrides after MBE or CVD growth, which is controlled by the intensity of heat applied for a given duration of time (e.g., application of a temperature of 600° C. to 900° C. for a duration of between 10 seconds to 10 hours), also affects the relationship between band gap and composition. This thermal annealing step may be performed in an atmosphere that includes air, nitrogen, arsenic, arsine, phosphorus, phosphine, hydrogen, forming gas, oxygen, helium and any combination of the preceding materials. In general, the band gap changes as thermal annealing parameters change. This is also true for doping profiles. The presence of dopants further complicates determination of the optimal combination of elements, growth parameters and thermal annealing conditions that will produce suitable high efficiency subcells having a specific band gap and vertical distribution of dopants.
Doping introduces an electric field in addition to the built-in electric field at the emitter-base junction of a subcell. The minority carriers generated by the photovoltaic effect in the subcell structure are affected by this additional electric field, influencing current collection. Positioning of a doping profile across a dilute nitride base layer can be designed to generate an optimized additional electric field that pushes minority carries to the front of the junction, resulting in a high recombination velocity and substantial improvement in minority carrier collection. This disclosure describes dilute nitride subcells with improved performance characteristics due to graded doping, where the dopant concentration changes with the vertical axis of a subcell. The doping profile may not be constant, but may be linear, exponential or have other dependence on position, causing different effects on the electric field. When dilute nitride subcells with graded doping are compared to conventional photovoltaic subcells with a wide, uniform region of intrinsic doping (i.e., undoped), for enhanced carrier collection (an accepted best practice for work with conventional semiconductor materials), graded doping dilute nitride subcells, and in particular exponentially doped dilute nitride subcells, exhibit superior performance characteristics. Position-dependent doping can also be applied to the emitter, further increasing current collection for the subcell when used in conjunction with doping of the dilute nitride base.
Various metrics can be used to characterize the quality of a dilute nitride subcell including, for example, the Eg/q-Voc, the efficiency over a range of irradiance energies, the open circuit voltage Voc and the short circuit current density Jsc. The open circuit voltage Voc and short circuit current density Jsc can be measured on subcells having a dilute nitride base layer with a thickness within the range from 1 μm to 4 μm. Those skilled in the art can understand how to extrapolate the open circuit voltage Voc and short circuit current density Jsc measured for a subcell having a particular dilute nitride base thickness to other subcell thicknesses. The Jsc and the Voc are the maximum current density and voltage, respectively, from a photovoltaic cell. However, at both of these operating points, the power from the photovoltaic cell is zero. The fill factor (FF) is a parameter which, in conjunction with Jsc and Voc, determines the maximum power from a photovoltaic cell. The FF is defined as the ratio of the maximum power produced by the photovoltaic cell to the product of Voc and Isc. Graphically, the FF is a measure of the “squareness” of the photovoltaic cell and is also the area of the largest rectangle which will fit within the IV curve. Graded doping subcells have improved values for Jsc, Voc, and FF.
The thickness of each layer forming a subcell, or a photodetector, can vary in order to optimize current and voltage outputs of the subcell, or the photocurrent produced by a photodetector. This is especially true for the optimal thickness of the dilute nitride base layer 106, where optimal thickness is different for each type of dilute nitride alloy as thickness must change with varying elemental composition. The dilute nitride base 106 and the (In)GaAs emitter 108 can have doping profiles that are linear, exponential, or constant. In some embodiments, the dopant concentration in the dilute nitride base 106 increases linearly or exponentially from the (In)GaAs emitter 108 to the (In)GaAs back surface field 104. In some embodiments, the (In)GaAs emitter 108 has a constant doping profile.
In some embodiments, such as device 200 shown in
In
In characterizing doping profiles, a constant doping profile refers to a semiconductor layer which is intentionally doped to have a certain concentration of dopant across the thickness of the layer. For example, a semiconductor layer such as the (In)GaAs emitter layer can be doped with a p-type dopant that is, for example, within 1%, within 5%, or within 10% of a nominal concentration. A constant doping concentration refers to a doping concentration that varies less than 1%, less than 5%, or less than 10% from a nominal dopant concentration across the thickness of a layer. For a constant doping profile, a target doping concentration may be intended that nevertheless may vary due to experimental conditions. An exponential doping profile is characterized by a dopant concentration across a layer or portion of a layer that increases exponentially from a beginning dopant concentration to a final dopant concentration. An exponential dopant concentration may increase by one, two, or in certain embodiments, three orders of magnitude across a layer. Again, an exponential dopant concentration may deviate from a true exponential profile due to experimental conditions. A linear doping profile refers to a doping profile that linearly increases across the thickness of a layer.
A practitioner skilled in the art understands that other types of layers may be incorporated or omitted in a photovoltaic cell to create a functional device and are not described here in detail. Briefly, these other types of layers include, for example, coverglass, anti-reflection coating, contact layers, front surface field, tunnel junctions, electrical contacts and a substrate or wafer handle. Each of these layers requires design and selection to ensure that its incorporation into a multijunction photovoltaic cell does not impair high performance. For example, a front-surface field layer may overly or be adjacent to an emitter layer (108, 208, 308) shown in
A dilute nitride optical absorber layer (or base layer) can be incorporated into dilute nitride-containing multijunction photovoltaic cells with differing numbers of junctions or subcells (see for example
As discussed herein,
By convention in the photovoltaic cell and photodetector art, the term “front” refers to the exterior surface of the cell (photodetector) that faces the radiation source, and the term “back” refers to the exterior surface that is away from the source. As used in the figures and descriptions, “back” is synonymous with “bottom” and “front” is synonymous with “top.”
An example of a graded doping profile for a dilute nitride optical absorber shown in
Doping=A×eBx;
where A=1×1015/cm3 to 2×1017/cm3, B=0.1/μm to 10/μm and x is depth. Using this range would yield doping between 1×1015/cm3and 1×1019/cm3 depending on the base thickness. In each case, the dopant flux is minimum at the emitter/base junction (the interface between 108 and 106). The value of the flux is preset to attain a desired value of the dopant concentration in the epitaxial layer. In this example, the thicknesses for the layers shown are 100 nm to 500 nm for back surface field layer 104, from 1000 nm to 2000 nm for dilute nitride optical absorber 106, and from 100 nm to 200 nm for emitter layer 108. An additional front-surface field layer can overly and be adjacent to the emitter layer 108 and can have a thickness between 10 nm and 500 nm, or between 10 nm and 100 nm.
Referring to
Doping=A;
where A is a constant and ranges from 0 to 2×1017/cm3. When there is no deliberate doping, the doping level in 206A may be an intrinsic or an unintentional doping level, which may be between about 1×1015/cm3and 1×1016/cm3. The remainder of the base (206A) has a doping profile that varies as a function of position in a manner similar to that explained for the previously described embodiment and as illustrated by the dotted line in sub-region 4 of this figure. Using this would yield doping between 1×1015/cm3and 1×1019/cm3 in the base for a thickness of 0 μm to 3 μm of the base.
The thickness of each sub-region can be varied in order to optimize the current and voltage output of the sub-cell. In particular, the optimal thicknesses will be different for different dilute nitride materials, and as the composition of the dilute nitride material changes. An example of such a doping profile is shown in
In the embodiment of the invention discussed above, the variations in doping profile are achieved during epitaxial growth of the semiconductor layers. In addition to the creation of the preferred doping profile during epitaxial growth, the profile may also be manipulated by post growth steps on the semiconductor epilayer. Such post-growth steps include but are not limited to annealing the semiconductor material in an atmosphere comprising one or more of the following: As, P, H2, N2, forming gas, and/or O2. Such a process step has multiple variables that must be optimized to achieve a desired doping profile. This includes but is not limited to changing the anneal time, anneal temperature, anneal cycle in addition to anneal environment mentioned above. For example, the anneal temperature may be between 400° C. and 1,000° C., while the duration of the annealing process may lie between 10 sec and 1000 sec, and the ambient condition can be a constant pressure atmosphere of primarily phosphorus, arsenic, hydrogen, oxygen and/or nitrogen. The final objective, irrespective of the process step used to achieve it, is a desirable doping profile for a certain composition of the dilute nitride material.
In still another embodiment of this invention, graded doping is introduced in the emitter of the dilute nitride solar cell. In this embodiment, the base may or may not have a graded doping profile according to the embodiments described above. The doping concentration of the emitter (layer 2 in
Referring to
In some embodiments, a dilute nitride subcell with an exponential doping profile in the second base portion 206A exhibits improved performance characteristics.
For the GaInNAsSb subcells presented in
As shown in
With Be as the dopant, several doping profiles were analyzed for improvement in dilute nitride subcell performance.
When considered together, the results presented in
As shown in
Referring to
The dilute nitride subcell can overly an n-type Ge or n-type GaAs substrate 302. The (In)GaAs emitter 308 can have a constant p-type dopant concentration, for example, within a range from 2E17 atoms/cm3 to 8E18 atoms/cm3, from 4E17 atoms/cm3 to 6E18 atoms/cm3, from 6E17 atoms/cm3 to 4E18 atoms/cm3, from 8E17 atoms/cm3 to 2E18 atoms/cm3, from 2E17 atoms/cm3 to 1E18 atoms/cm3, or within a range from 1E18 atoms/cm3 to 8E18 atoms/cm3. The base portion 306 may or may not include a first base portion. Embodiments in which the first base portion has a thickness of 0 nm means that the first base portion is absent. The first base portion can have an intrinsic level of dopant such as, for example, within a range of 5E15 atoms/cm3 to 5E16 atoms/cm3. The second base portion can have an exponential doping profile that increases from the first base portion (or if the first base portion is absent, from the emitter) to the back surface field 304. The concentration of the n-type dopant at the interface with the first base portion, or the emitter, can be an intrinsic doping concentration such as, for example, within the range from 5E15 atoms/cm3 to 5E16 atoms/cm3, from 5E15 atoms/cm3 to 1E16 atoms/cm3, from 1E16 atoms/cm3 to 5E16 atoms/cm3, or within the range from 8E15 atoms/cm3 to 2E16 atoms/cm3. At the interface with the back surface field, the p-type dopant concentration can be within the range, for example, of 1E17 atoms/cm3 to 8E18 atoms/cm3, from 3E17 atoms/cm3 to 6E18 atoms/cm3 from 5E17 atoms/cm3to 4E18 atoms/cm3, from 7E17 atoms/cm3to 2E18 atoms/cm3, from 1E17 atoms/cm3to 1E18 atoms/cm3, or within the range from 1E18 atoms/cm3 to 8E18 atoms/cm3. The back surface field can be p-type doped at a concentration within a range from 0.1E18 atoms/cm3 to 8E18 atoms/cm3. In certain embodiments, the concentration of the n-type dopant in the second base portion can exponentially increase by one order of magnitude, for example, from 1E16 atoms/cm3 to 1E17 atoms/cm3, or from 5E16 atoms/cm3 to 5E17 atoms/cm3. In certain embodiments, the concentration of the p-type dopant in the second base portion can increase, for example, from 5E15 atoms/cm3 to 1E17 atoms/cm3, from 5E15 atoms/cm3 to 5E17 atoms/cm3, from 5E15 atoms/cm3 to 1E18 atoms/cm3, or from 5E15 atoms/cm3 to 5E18 atoms/cm3; from 1E16 atoms/cm3 to 1E17 atoms/cm3, from 1E16 atoms/cm3 to 5E17 atoms/cm3, from 1E16 atoms/cm3 to 1E18 atoms/cm3, or from 1E16 atoms/cm3 to 5E18 atoms/cm3; from 5E16 atoms/cm3 to 1E17 atoms/cm3, from 5E16 atoms/cm3 to 5E17 atoms/cm3, from 5E16 atoms/cm3to 1E18 atoms/cm3, or can increase from 5E16 atoms/cm3 to 5E18 atoms/cm3.
Doped dilute nitride materials provided by the present disclosure can be incorporated as dilute nitride subcells into multijunction photovoltaic cells such as 3-junction, 4-junction, 5-junction, and 6-junction multijunction photovoltaic cells. When the dilute nitride subcell is the current limiting subcell of a multijunction cell, the efficiency of the multijunction photovoltaic cell will improve by about the same amount as the improvement in the efficiency of the dilute nitride subcell. For example, a 1% improvement in the efficiency of a rate-limiting dilute nitride subcell will result in an improvement in the multijunction photovoltaic cell efficiency of about 1%.
Seemingly small improvements in the efficiency of a dilute nitride subcell can result in significant improvements in the efficiency of a multijunction photovoltaic cell. Again, seemingly small improvements in the overall efficiency of a multijunction photovoltaic cell can result in dramatic improvements in output power, reduce the area of a photovoltaic array, and reduce costs associated with installation, system integration, and deployment.
Photovoltaic cell efficiency is important as it directly affects the photovoltaic module power output. For example, assuming a 1 m2 photovoltaic panel having an overall 24% conversion efficiency, if the efficiency of multi junction photovoltaic cells used in a module is increased by 1% such as from 40% to 41% under 500 suns, the module output power will increase by about 2.7 KW.
Normally a photovoltaic cell contributes around 20% to the total cost of a photovoltaic power module. Higher photovoltaic cell efficiency means more cost-effective modules. Fewer photovoltaic devices are then needed to generate the same amount of output power, and higher power with fewer devices leads to reduces system costs, such as costs for mounting racks, hardware, wiring for electrical connections, etc. In addition, by using high efficiency photovoltaic cells, to generate the same power, less land area, fewer support structures, and lower labor costs are required for installation.
Photovoltaic modules are a significant component in spacecraft power systems. Lighter weight and smaller photovoltaic modules are always preferred because the lifting cost to launch satellites into orbit is expensive. Photovoltaic cell efficiency is especially important for space power applications to reduce the mass and fuel penalty due to large photovoltaic arrays. The higher specific power (watts generated over photovoltaic array mass), which indicates how much power one array will generate for a given launch mass, can be achieved with more efficient photovoltaic cells since the size and weight of the photovoltaic array would be less for getting the same power output.
As an example, compared to a nominal photovoltaic cell having a 30% conversion efficiency, a 1.5% increase in multijunction photovoltaic cell efficiency can result in a 4.5% increase in output power, and a 3.5% increase in multijunction photovoltaic cell efficiency can result in an increase a 11.5% increase in output power. For a satellite having a 60 kW power requirement, the use of higher efficiency subcells can result in photovoltaic cell module cost savings from $0.5 million to $1.5 million, and a reduction in photovoltaic array surface area of 6.4 m2 to 15.6 m2, for multijunction photovoltaic cells having increased efficiencies of 1.5% and 3.5%, respectively. The overall cost savings will be even greater when costs associated with system integration and launch are taken into consideration.
Exponentially doped dilute nitride subcells can be incorporated into multijunction photovoltaic cells. Examples of multijunction photovoltaic cells are disclosed in U.S. Application Publication No. 2013/0130431, U.S. Application Publication No. 2013/0118566, and in U.S. Application Publication No. 2017/0110613, each of which is incorporated by reference in its entirety.
GaInNAsSb semiconductor materials are advantageous as photovoltaic cell materials because the lattice constant can be varied to be substantially matched to a broad range of substrates and/or subcells formed from other than GaInNAsSb materials. The present invention includes multijunction photovoltaic cells with three or more subcells such as three-, four- and five junction subcells incorporating at least one Ga1-xInxNyAs1-y-zSbz subcell. For example, Ga1-xInxNyAs1-y-zSbz, disclosed in U.S. Application Publication No. 2010/0319764, can produce a high-quality material when substantially lattice-matched to a GaAs or Ge substrate in the composition range of 0.08≤x≤0.18, 0.025≤y≤0.04 and 0.001≤z≤0.03, with a band gap of at least 0.9 eV.
The band gaps of the Ga1-xInxNyAs1-y-zSbz materials can be in part tailored by varying the composition while controlling the overall composition of Sb. Thus, Ga1-xInxNyAs1-y-zSbz subcell with a band gap suitable for integrating with the other subcells may be fabricated while maintaining substantial lattice-matching to the other subcells. The band gaps and compositions of the Ga1-xInxNyAs1-y-zSbz subcells can be tailored so that the short-circuit current produced by the Ga1-xInxNyAs1-y-zSbz subcells will be the same as or slightly greater than the short-circuit current of the other subcells in the photovoltaic cell. Because Ga1-xInxNyAs1-y-zSbz materials provide high quality, lattice-matched and band gap tunable subcells, the disclosed photovoltaic cells comprising Ga1-xInxNyAs1-y-zSbz subcells can achieve high conversion efficiencies. The increase in efficiency is largely due to less light energy being lost as heat, as the additional subcells allow more of the incident photons to be absorbed by semiconductor materials with band gaps closer to the energy level of the incident photons. In addition, there will be lower series resistance losses in these multijunction photovoltaic cells compared with other photovoltaic cells due to the lower operating currents. At higher concentrations of sunlight, the reduced series resistance losses become more pronounced. Depending on the band gap of the bottom subcell, the collection of a wider range of photons in the solar spectrum may also contribute to the increased efficiency.
Designs of multijunction photovoltaic cells with more than three subcells in the prior art predominantly rely on metamorphic growth structures, new materials, or dramatic improvements in the quality of existing subcell materials in order to provide structures that can achieve high efficiencies. Photovoltaic cells containing metamorphic buffer layers may have reliability concerns due to the potential for dislocations originating in the buffer layers to propagate over time into the subcells, causing degradation in performance. In contrast, Ga1-xInxNyAs1-y-zSbz materials can be used in lattice matched photovoltaic cells with more than three subcells to attain high efficiencies while maintaining substantial lattice-matching between subcells, which is advantageous for reliability. For example, reliability testing on Ga1-xInxNyAs1-y-zSbz subcells provided by the present disclosure has shown that multijunction photovoltaic cells comprise a Ga1-xInxNyAs1-y-zSbz subcell, such devices can survive the equivalent of 390 years of on-sun operation at 100° C. with no failures. The maximum degradation observed in these subcells was a decrease in open-circuit voltage of about 1.2%.
For application in space, radiation hardness, which refers to minimal degradation in device performance when exposed to ionizing radiation including electrons and protons, is of great importance. Multijunction photovoltaic cells incorporating Ga1-xInxNyAs1-y-zSbz subcells provided by the present disclosure have been subjected to proton radiation testing to examine the effects of degradation in space environments. Compared to Ge-based triple junction photovoltaic cells, the results demonstrate that these Ga1-xInxNyAs1-y-zSbz containing devices have similar power degradation rates and superior voltage retention rates. Compared to non-lattice matched (metamorphic) triple junction photovoltaic cells, all metrics are superior for Ga1-xInxNyAs1-y-zSbz containing devices. In certain embodiments, the photovoltaic cells include (Al) InGaP subcells to improve radiation hardness compared to (Al,In)GaAs subcells.
Due to interactions between the different elements, as well as factors such as the strain in the layer, the relationship between composition and band gap for Ga1-xInxNyAs1-y-zSbz is not a simple function of composition. The composition that yields a desired band gap with a specific lattice constant can be found by empirically varying the composition.
The thermal dose applied to the Ga1-xInxNyAs1-y-zSbz material, which is controlled by the intensity of heat applied for a given duration of time (e.g., application of a temperature of 600° C. to 900° C. for a duration of between 10 seconds to 10 hours), that a Ga1-xInxNyAs1-y-zSbz material receives during growth and after growth, also affects the relationship between band gap and composition. In general, the band gap increases as thermal dose increases.
As the composition is varied within the Ga1-xInxNyAs1-y-zSbz material system, the growth conditions need to be modified. For example, for (Al,In)GaAs, the growth temperature will increase as the fraction of Al increases and decrease as the fraction of In increases, in order to maintain the same material quality. Thus, as a composition of either the Ga1-xInxNyAs1-y-zSbz material or the other subcells of the multijunction photovoltaic cell is changed, the growth temperature as well as other growth conditions can be adjusted accordingly.
Schematic diagrams of the three junction, four junction, and five junction photovoltaic cells are shown
In the example shown in
The specific band gaps of the subcells, within the ranges given in the preceding as well as subsequent embodiments, are dictated, at least in part, by the band gap of the bottom subcell, the thicknesses of the subcell layers, and the incident spectrum of light. Although there are numerous structures in the present disclosure that will produce efficiencies exceeding those of three junction photovoltaic cells, it is not the case that any set of subcell band gaps that falls within the disclosed ranges will produce an increased photovoltaic conversion efficiency. For a certain choice of bottom subcell band gap, or alternately the band gap of another subcell, incident spectrum of light, subcell materials, and subcell layer thicknesses, there is a narrower range of band gaps for the remaining subcells that will produce efficiencies exceeding those of other three junction photovoltaic cells.
In each of the embodiments described herein, the tunnel junctions are designed to have minimal light absorption. Light absorbed by tunnel junctions is not converted into electricity by the photovoltaic cell, and thus if the tunnel junctions absorb significant amounts of light, it will not be possible for the efficiencies of the multijunction photovoltaic cells to exceed those of the best triple junction photovoltaic cells. Accordingly, the tunnel junctions must be very thin (preferably less than 40 nm) and/or be made of materials with band gaps equal to or greater than the subcells immediately above the respective tunnel junction. An example of a tunnel junction fitting these criteria is a GaAs/AlGaAs tunnel junction, where each of the GaAs and AlGaAs layers forming the tunnel junction has a thickness between 5 nm and 15 nm. The GaAs layer can be doped with Te, Se, S and/or Si, and the AlGaAs layer can be doped with C.
In each of the embodiments described and illustrated herein, additional semiconductor layers are present in order to create a photovoltaic cell device. Specifically, cap or contact layer(s), anti-reflection coating (ARC) layers and electrical contacts (also denoted as the metal grid) can be formed above the top subcell, and buffer layer(s), the substrate or handle, and bottom contacts can be formed or be present below the bottom subcell. In certain embodiments, the substrate may also function as the bottom subcell, such as in a Ge subcell. Other semiconductor layers, such as additional tunnel junctions, may also be present. Multijunction photovoltaic cells may also be formed without one or more of the elements listed above, as known to those skilled in the art.
In operation, a multijunction photovoltaic cell is configured such that the subcell having the highest band gap faces the incident photovoltaic radiation, with subcells characterized by increasingly lower band gaps situated underlying or beneath the uppermost subcell.
In the embodiments disclosed herein, each subcell may comprise several layers. For example, each subcell may comprise a window layer, an emitter, a base, and a back surface field (BSF) layer.
In operation, the window layer is the topmost layer of a subcell and faces the incident radiation. In certain embodiments, the thickness of a window layer can be, for example, from about 10 nm to about 500 nm, from about 10 nm to about 300 nm, from about 10 nm to about 150 nm, and in certain embodiments, from about 10 nm to about 50 nm. In certain embodiments, the thickness of a window layer can be, for example, from about 50 nm to about 350 nm, from about 100 nm to about 300 nm, and in certain embodiments, from about 50 nm to about 150 nm.
In certain embodiments, the thickness of an emitter layer can be, for example, from about 10 nm to about 300 nm, from about 20 nm to about 200 nm, from about 50 nm to about 200 nm, and in certain embodiments, from about 75 nm to about 125 nm.
In certain embodiments, the thickness of a base layer can be, for example, from about 0.1 μm to about 6 μm, from about 0.1 μm to about 4 μm, from about 0.1 μm to about 3 μm, from about 0.1 μm to about 2 μm, and in certain embodiments, from about 0.1 μm to about 1 μm. In certain embodiments, the thickness of a base layer can be, for example, from about 0.5 μm to about 5 μm, from about 1 μm to about 4 μm, from about 1.5 μm to about 3.5 μm, and in certain embodiments, from about 2 μm to about 3 μm.
In certain embodiments the thickness of a BSF layer can be from about 10 nm to about 500 nm, from about 50 nm to about 300 nm, and in certain embodiments, from about 50 nm to about 150 nm.
In certain embodiments, an (Al)InGaP subcell comprises a window comprising AlInP, an emitter comprising (Al)InGaP, a base comprising (Al)InGaP, and a back surface field layer comprising AlInGaP.
In certain embodiments, an (Al)InGaP subcell comprises a window comprising AlInP having a thickness from 10 nm to 50 nm, an emitter comprising (Al)InGaP having a thickness from 20 nm to 200 nm, a base comprising (Al)InGaP having a thickness from 0.1 μm to 2 μm, and a BSF layer comprising AlInGaP having a thickness from 50 nm to 300 nm.
In certain of such embodiments, an (Al)InGaP subcell is characterized by a band gap within a range from about 1.9 eV to about 2.2 eV.
In certain embodiments, an (Al,In)GaAs subcell comprises a window comprising (Al)In(Ga)P or (Al,In)GaAs, an emitter comprising (Al)InGaP or (Al,In)GaAs, a base comprising (Al,In)GaAs, and a BSF layer comprising (Al,In)GaAs or (Al)InGaP. In certain embodiments, an (Al,In)GaAs subcell comprises a window comprising (Al)InGaP having a thickness from 50 nm to 400 nm, an emitter comprising (Al,In)GaAs having a thickness from 100 nm to 200 nm, a base comprising (Al,In)GaAs having a thickness from 1 μm to 4 μm, and a BSF layer comprising (Al,In)GaAs having a thickness from 100 nm to 300 nm.
In certain embodiments, an (Al,In)GaAs subcell comprises a window comprising (Al)InGaP having a thickness from 200 nm to 300 nm, an emitter comprising (Al,In)GaAs having a thickness from 100 nm to 150 nm, a base comprising (Al,In)GaAs having a thickness from 2 μm to 3.5 μm, and a BSF layer comprising (Al,In)GaAs having a thickness from 150 nm to 250 nm.
In certain of such embodiments, an (Al,In)GaAs subcell is characterized by a band gap within a range from about 1.4 eV to about 1.7 eV.
In certain embodiments, an (Al) InGaAsP subcell comprises a window comprising (Al)In(Ga)P, an emitter comprising (Al) InGaP or (Al) InGaAsP, a base comprising (Al) InGaAsP, and a BSF layer comprising (Al,In)GaAs or (Al)InGaP. In certain embodiments, an (Al) InGaAsP subcell comprises a window comprising (Al)In(Ga)P having a thickness from 50 nm to 300 nm, an emitter comprising (Al)InGaP or (Al) InGaAsP having a thickness from 100 nm to 200 nm, a base comprising (Al) InGaAsP having a thickness from 0.5 μm to 4 μm, and a BSF layer comprising Al(In)GaAs or (Al)InGaP having a thickness from 50 nm to 300 nm.
In certain of such embodiments, an (Al)InGaAsP subcell is characterized by a band gap within a range from about 1.4 eV to about 1.8 eV.
In certain embodiments, a Ga1-xInxNyAs1-y-zSbz subcell comprises a window comprising (Al)InGaP or (Al,In)GaAs, an emitter comprising (In)GaAs or a Ga1-xInxNyAs1-y-zSbz, a base comprising a Ga1-xInxNyAs1-y-zSbz, and a BSF layer comprising (In)GaAs.
In certain embodiments, a Ga1-xInxNyAs1-y-zSbz subcell comprises a window comprising (Al)InGaP or (In)GaAs, having a thickness from 0 nm to 300 nm, an emitter comprising (In)GaAs or a Ga1-xInxNyAs1-y-zSbz alloy having a thickness from 100 nm to 200 nm, a base comprising a Ga1-xInxNyAs1-y-zSbz having a thickness from 1 μm to 4 μm, and a BSF layer comprising (In)GaAs having a thickness from 50 nm to 300 nm. In certain embodiments, a Ga1-xInxNyAs1-y-zSbz alloy subcell comprises an emitter comprising InGaAs or a III-AsNV alloy having a thickness from 100 nm to 150 nm, a base comprising a Ga1-xInxNyAs1-y-zSbz alloy having a thickness from 2 μm to 3 μm, and a BSF layer comprising (In)GaAs having a thickness from 50 nm to 200 nm.
In certain of such embodiments, a Ga1-xInxNyAs1-y-zSbz subcell is characterized by a band gap within a range from about 0.7 to about 1.1 eV, or within a range from about 0.9 eV to about 1.3 eV. In certain of such embodiments, the Ga1-xInxNyAs1-y-zSbz subcell is a GaInNAsSb subcell.
In certain of such embodiments, a Ga1-xInxNyAs1-y-zSbz subcell has a compressive strain of less than 0.6%, meaning that the in-plane lattice constant of the Ga1-xInxNyAs1-y-zSbz material in its fully relaxed state is between 0.0% and 0.6% greater than that of the substrate. In certain of such embodiments, the Ga1-xInxNyAs1-y-zSbz subcell contains Sb and does not contain Bi.
In certain embodiments, a Ge subcell comprises a window comprising (Al)InGaP or (Al,In)GaAs, having a thickness from 0 nm to 300 nm, an emitter comprising (Al,In)GaAs, (Al,Ga)InP, or Ga1-xInxNyAs1-y-zSbz, having a thickness from 10 nm to 500 nm, and a base comprising the Ge substrate. It is to be noted that multijunction photovoltaic cells may also be formed on a Ge or GaAs substrate wherein the substrate is not part of a subcell.
In certain embodiments, one or more of the subcells has an emitter and/or a base in which there is a graded doping profile. The doping profile may be linear, exponential or with other dependence on position. In certain of such embodiments, one or more of the Ga1-xInxNyAs1-y-zSbz subcells has an exponential or linear doping profile over part or all of the base, with the doping levels between 1E15 atoms/cm3 and 1E19 atoms/cm3, or between 1E1016 atoms/cm3 and 5E18 atoms/cm3. Further, the region of the Ga1-xInxNyAs1-y-zSbz base that is closest to the emitter may have constant or no doping, as disclosed, for example, in U.S. Application Publication No. 2012/0103403, which is incorporated by reference in its entirety. Examples of dopants include, for example, Be, Mg, Zn, Te, Se, Si, C, and others known in the art.
A tunnel junction may be disposed between each of the subcells. Each tunnel junction comprises two or more layers that electrically connect adjacent subcells. The tunnel junction includes a highly doped n-type layer adjacent to a highly doped p-type layer to form a p-n junction. Typically, the doping levels in a tunnel junction are between 1E18 atoms/cm3 and 1E21 atoms/cm3.
In certain embodiments, a tunnel junction comprises an n-type (Al,In)GaAs or (Al)InGaP(As) layer and a p-type (Al,In)GaAs layer. In certain embodiments the dopant of the n-type layer comprises Si and the dopant of the p-type layer comprises C. A tunnel junction may have a thickness less than about 100 nm, less than 80 nm, less than 60 nm, less than 40 nm, and in certain embodiments, less than 20 nm. For example, in certain embodiments, a tunnel junction between (Al)InGaP subcells, between an (Al)InGaP subcell and an (Al,In)GaAs or (Al)InGaAsP subcell, or between (Al,In)GaAs subcells may have a thickness less than about 30 nm, less than about 20 nm, less than about 15 nm, and in certain embodiments, less than about 12 nm. In certain embodiments, a tunnel junction separating an (Al,In)GaAs and III-AsNV alloy subcell, separating adjacent III-AsNV alloy subcells, or separating a III-AsNV alloy and a (Si,Sn)Ge or Ge subcell may have a thickness less than 100 nm, less than 80 nm, less than 60 nm, and in certain embodiments, less than 40 nm.
A multijunction photovoltaic cell may be fabricated on a substrate such as a Ge substrate. In certain embodiments, the substrate can comprise GaAs, InP, Ge, or Si. In certain embodiments, all of the subcells are substantially lattice-matched to the substrate. In certain embodiments, one or more of the layers that are included within the completed photovoltaic cell but are not part of a subcell such as, for example, anti-reflective coating layers, contact layers, cap layers, tunnel junction layers, and buffer layers, are not substantially lattice-matched to the subcells.
In certain embodiments, the multijunction photovoltaic cell comprises an anti-reflection coating overlying the uppermost subcell. The materials comprising the anti-reflection coating and the thickness of the anti-reflection coating are selected to improve the efficiency of light capture in the multijunction photovoltaic cell. In certain embodiments, one or more contact layers overlie the uppermost subcell in the regions underlying or near the metal grid. In certain embodiments, the contact layers comprise (In)GaAs and the dopant may be Si or Be.
Dilute nitride-containing multijunction photovoltaic cells such as GaInNAsSb-containing multijunction photovoltaic cells provided by the present disclosure may be incorporated into a photovoltaic power system. A photovoltaic power system can comprise one or more photovoltaic cells provided by the present disclosure such as, for example, one or more photovoltaic cells having at least three, at least four subcells or at least five subcells, including one or more GaInNAsSb subcells. In certain embodiments, the one or more photovoltaic cells have a GaInNAsSb subcell as the bottom subcell or the subcell immediately above the bottom subcell. In certain embodiments, the photovoltaic power system may be a concentrating photovoltaic system, wherein the system may also comprise mirrors and/or lenses used to concentrate sunlight onto one or more photovoltaic cells. In certain embodiments, the photovoltaic power system comprises a single or dual axis tracker. In certain embodiments, the photovoltaic power system is designed for portable applications, and in other embodiments, for grid-connected power generation. In certain embodiments, the photovoltaic power system is designed to convert a specific spectrum of light, such as AM1.5G, AM1.5D or AM0, into electricity. In certain embodiments, the photovoltaic power system may be found on satellites or other extra-terrestrial vehicles and designed for operation in space without the influence of a planetary atmosphere on the impinging light source. In certain embodiments, the photovoltaic power system may be designed for operation on astronomical bodies other than earth. In certain embodiments, the photovoltaic power system may be designed for satellites orbiting about astronomical bodies other than earth. In certain embodiments, the photovoltaic power system may be designed for roving on the surface of an astronomical body other than earth.
Photovoltaic modules are provided comprising one or more multijunction photovoltaic cells provided by the present disclosure. A photovoltaic module may comprise one or more photovoltaic cells provided by the present disclosure to include an enclosure and interconnects to be used independently or assembled with additional modules to form a photovoltaic power system. A module and/or power system may include power conditioners, power converters, inverters and other electronics to convert the power generated by the photovoltaic cells into usable electricity. A photovoltaic module may further include optics for focusing light onto a photovoltaic cell provided by the present disclosure such as in a concentrated photovoltaic module. Photovoltaic power systems can comprise one or more photovoltaic modules, such as a plurality of photovoltaic modules.
As disclosed, for example, in U.S. Application Publication No. 2017/0110613, high efficiency GaInNAsSb dilute nitride subcells have been fabricated. The efficiency of these GaInNAsSb subcells employ the doping profiles provided by the present disclosure such as, for example, exponential doping in the Ga1-xInxNyAs1-y-zSbz base or a combination of constant and exponential doping in the Ga1-xInxNyAs1-y-zSbz base.
Three-, four-, and five junction photovoltaic cells comprising at least one Ga1-xInxNyAs1-y-zSbz subcell have been fabricated. The ability to provide high efficiency Ga1-xInxNyAs1-y-zSbz-based photovoltaic cells is predicated on the ability to provide a high quality Ga1-xInxNyAs1-y-zSbz subcell that is lattice matched to other semiconductor layers including Ge and GaAs substrates and that can be tailored to have a band gap within the range from 0.8 eV to 1.3 eV.
Ga1-xInxNyAs1-y-zSbz subcells provided by the present disclosure are fabricated to provide a high efficiency. Factors that contribute to providing a high efficiency Ga1-xInxNyAs1-y-zSbz subcells include, for example, the band gaps of the individual subcells, which in turn depends on the semiconductor composition of the subcells, doping levels and doping profiles, thicknesses of the subcells, quality of lattice matching, defect densities, growth conditions, annealing temperatures and profiles, and impurity levels.
Various metrics can be used to characterize the quality of a GaInNAsSb subcell including, for example, the Eg/q-Voc, the efficiency over a range of irradiance energies, the open circuit voltage Voc and the short circuit current density Jsc. The open circuit voltage Voc and short circuit current Jsc can be measured on subcells having a Ga1-xInxNyAs1-y-zSbz base layer that is 2 μm thick or other thickness such as, for example, a thickness from 1 μm to 4 μm. Those skilled in the art would understand how to extrapolate the open circuit voltage Voc and short circuit current Jsc measured for a subcell having a particular Ga1-xInxNyAs1-y-zSbz base thickness to other thicknesses.
The quality of a Ga1-xInxNyAs1-y-zSbz subcell can be reflected by a curve of the efficiency as a function of irradiance wavelength or irradiance energy. In general, a high quality Ga1-xInxNyAs1-y-zSbz subcell exhibits an efficiency of at least 60%, at least 70% or at least 80% over a wide range of irradiance wavelengths.
The irradiance wavelengths for which the efficiencies of the Ga1-xInxNyAs1-y-zSbz subcell referred to in
The Ga1-xInxNyAs1-y-zSbz subcells measured in
As shown in
The Ga1-xInxNyAs1-y-zSbz subcells exhibited an efficiency as follows: an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.30 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.30 eV; an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.18 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.30 eV; an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.10 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.18 eV; an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.03 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.15 eV; an efficiency of at least 70% at an irradiance energy from 1.38 eV to 0.99 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.15 eV; or an efficiency of at least 60% at an irradiance energy from 1.38 eV to 0.92 eV, an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.03 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.15 eV; wherein the efficiency was measured at a junction temperature of 25° C.
Ga1-xInxNyAs1-y-zSbz subcells having a band gap between 1.18 eV and 1.24 eV, exhibited an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.30 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.30 eV, measured at a junction temperature of 25° C.
Ga1-xInxNyAs1-y-zSbz subcells having a band gap between 1.10 eV and 1.14 eV, exhibited an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.18 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.30 eV, measured at a junction temperature of 25° C.
Ga1-xInxNyAs1-y-zSbz subcells having a band gap between 1.04 eV and 1.06 eV, exhibited an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.10 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.18 eV, measured at a junction temperature of 25° C.
Ga1-xInxNyAs1-y-zSbz subcells having a band gap between 0.99 eV and 1.01 eV, exhibited an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.03 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.15 eV, measured at a junction temperature of 25° C.
Ga1-xInxNyAs1-y-zSbz subcells having a band gap between 0.90 eV and 0.98 eV, exhibited an efficiency of at least 70% at an irradiance energy from 1.38 eV to 0.99 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.15 eV, measured at a junction temperature of 25° C. Ga1-xInxNyAs1-y-zSbz subcells having a band gap between 0.80 eV and 0.86 eV, exhibited an efficiency of at least 60% at an irradiance energy from 1.38 eV to 0.92 eV, an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.03 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.15 eV, measured at a junction temperature of 25° C.
The Ga1-xInxNyAs1-y-zSbz subcells also exhibited an efficiency as follows: an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.27 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.30 eV; an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.18 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.30 eV; an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.10 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.18 eV; an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.03 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.13 eV; or an efficiency of at least 60% at an irradiance energy from 1.38 eV to 0.92 eV, an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.03 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.08 eV; wherein the efficiency is measured at a junction temperature of 25° C.
Ga1-xInxNyAs1-y-zSbz subcells having a band gap between 1.18 eV and 1.24 eV, exhibited an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.27 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.30 eV, measured at a junction temperature of 25° C.
Ga1-xInxNyAs1-y-zSbz subcells having a band gap between 1.10 eV and 1.14 eV, exhibited an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.18 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.30 eV, measured at a junction temperature of 25° C.
Ga1-xInxNyAs1-y-zSbz subcells having a band gap between 1.04 eV and 1.06 eV, exhibited an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.10 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.18 eV, measured at a junction temperature of 25° C.
Ga1-xInxNyAs1-y-zSbz subcells having a band gap between 0.94 eV and 0.98 eV, exhibited an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.03 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.13 eV, measured at a junction temperature of 25° C.
Ga1-xInxNyAs1-y-zSbz subcells having a band gap between 0.80 eV and 0.90 eV, exhibited an efficiency of at least 60% at an irradiance energy from 1.38 eV to 0.92 eV, an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.03 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.08 eV, measured ata junction temperature of 25° C.
The Ga1-xInxNyAs1-y-zSbz subcells exhibited an Eg/q-Voc of at least 0.55 V, at least 0.60 V, or at least 0.65 V over each respective range of irradiance energies listed in the preceding paragraphs. The Ga1-xInxNyAs1-y-zSbz subcells exhibited an Eg/q-Voc within the range of 0.55 V to 0.70 V over each respective range of irradiance energies listed in the preceding paragraphs.
A Ga1-xInxNyAs1-y-zSbz subcell can be characterized by a band gap of about 1.24 eV, an efficiency greater than 70% at irradiance energies from about 1.27 eV to about 1.38 eV and an efficiency greater than 80% at irradiance energies from about 1.33 eV to about 1.38 eV.
A Ga1-xInxNyAs1-y-zSbz subcell can be characterized by a band gap of about 1.14 eV, an efficiency greater than 70% at irradiance energies from about 1.24 eV to about 1.38 eV and an efficiency greater than 80% at irradiance energies from about 1.30 eV to about 1.38 eV.
A Ga1-xInxNyAs1-y-zSbz subcell can be characterized by a band gap of about 1.10 eV, an efficiency greater than 70% at irradiance energies from about 1.18 eV to about 1.38 eV and an efficiency greater than 80% at irradiance energies from about 1.30 eV to about 1.38 eV.
A Ga1-xInxNyAs1-y-zSbz subcell can be characterized by a band gap of about 1.05 eV, an efficiency greater than 70% at irradiance energies from about 1.13 eV to about 1.38 eV and an efficiency greater than 80% at irradiance energies from about 1.18 eV to about 1.38 eV.
A Ga1-xInxNyAs1-y-zSbz subcell can be characterized by a band gap of about 1.00 eV, an efficiency greater than 70% at irradiance energies from about 1.08 eV to about 1.38 eV and an efficiency greater than 80% at irradiance energies from about 1.13 eV to about 1.38 eV.
A Ga1-xInxNyAs1-y-zSbz subcell can be characterized by a band gap of about 0.96 eV, an efficiency greater than 70% at irradiance energies from about 1.03 eV to about 1.38 eV and an efficiency greater than 80% at irradiance energies from about 1.13 eV to about 1.38 eV.
A Ga1-xInxNyAs1-y-zSbz subcell can be characterized by a band gap of about 0.82 eV, an efficiency greater than 70% at irradiance energies from about 0.99 eV to about 1.38 eV and an efficiency greater than 80% at irradiance energies from about 1.13 eV to about 1.38 eV.
The quality of a Ga1-xInxNyAs1-y-zSbz subcell is reflected in a high short circuit current density Jsc, a low open circuit voltage Voc, a high fill factor, and a high efficiency over a broad range of irradiance wavelengths/energies.
These parameters are provided for certain Ga1-xInxNyAs1-y-zSbz subcells having a band gap from 0.907 eV to 1.153 eV in Table 2.
In Table 2, FF refers to the fill factor and PL BG refers to the band gap as measured using photoluminescence.
For each of the Ga1-xInxNyAs1-y-zSbz subcells presented in Table 2, the efficiency (EQE) was about 87% and the efficiency was about 89% at a junction temperature of 25° C. The dependence of the efficiencies as a function of irradiance energy for subcells B, C, and D. Ga1-xInxNyAs1-y-zSbz subcells are shown in
The efficiencies for Ga1-xInxNyAs1-y-zSbz subcells B, C, and D are presented in graphical form in
As shown in
Also, as shown in
The quality of the Ga1-xInxNyAs1-y-zSbz compositions provided by the present disclosure is also reflected in the low open circuit voltage Voc, which depends in part on the band gap of the Ga1-xInxNyAs1-y-zSb z composition. The dependence of the open circuit voltage Voc with the band gap of the Ga1-xInxNyAs1-y-zSbz composition is shown in
Ga1-xInxNyAs1-y-zSbz subcells exhibiting a band gap from 0.90 eV to 1.2 eV can have values for x, y, and z of 0.010≤x≤0.18, 0.015≤y≤0.083, 0.004≤z≤0.018. A summary of the element content, band gap, short circuit current density Jsc and open circuit voltage Voc for certain Ga1-xInxNyAs1-y-zSbz subcells is presented in Table 4.
In Table 3, the short circuit current density Jsc and open circuit voltage Voc were measured using a 1 sun AM1.5D spectrum at a junction temperature of 25° C. The Ga1-xInxNyAs1-y-zSbz subcells were 2 μm thick.
In certain embodiments, a Ga1-xInxNyAs1-y-zSbz subcell can be characterized by a Eg/q-Voc equal to or greater than 0.55 V measured using a 1 sun AM1.5D spectrum at a junction temperature of 25° C.
In certain embodiments, a Ga1-xInxNyAs1-y-zSbz subcell can be characterized by a Eg/q-Voc from 0.4 V to 0.7 V measured using a 1 sun AM1.5D spectrum at a junction temperature of 25° C.
In certain embodiments, a Ga1-xInxNyAs1-y-zSbz subcell can have values for x, y, and z of 0.016≤x≤0.19, 0.040≤y≤0.051, and 0.010≤z≤0.018; a band gap within the range from 0.89 eV to 0.92 eV; a short circuit current density Jsc greater than 15 mA/cm2; and an open circuit voltage Voc greater than 0.3 V. In such embodiments, the Ga1-xInxNyAs1-y-zSbz subcells can exhibit an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.03 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.13 eV, measured at a junction temperature of 25° C.
In certain embodiments, a Ga1-xInxNyAs1-y-zSbz subcell can have values for x, y, and z of 0.010≤x≤0.16, 0.028≤y≤0.037, and 0.005≤z≤0.016; and a band gap within the range from 0.95 eV to 0.98 eV. In such embodiments, the Ga1-xInxNyAs1-y-zSbz subcells can exhibit an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.03 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.13 eV, measured at a junction temperature of 25° C.
In certain embodiments, a Ga1-xInxNyAs1-y-zSbz subcell can have values for x, y, and z of 0.075≤x≤0.081, 0.040≤y≤0.051, and 0.010≤z≤0.018; a band gap within the range from 1.111 eV to 1.117 eV; a short circuit current density Jsc greater than 9 mA/cm2; and an open circuit voltage Voc greater than 0.4 V. In such embodiments, the Ga1-xInxNyAs1-y-zSbz subcells can exhibit an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.18 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.30 eV, measured at a junction temperature of 25° C.
In certain embodiments, a Ga1-xInxNyAs1-y-zSbz subcell can have values for x, y, and z of 0.016≤x≤0.024, 0.077≤y≤0.085, and 0.011≤z≤0.015; a band gap within the range from 1.10 eV to 1.14 eV; a short circuit current density Jsc greater than 9 mA/cm2; and an open circuit voltage Voc greater than 0.4 V. In such embodiments, the Ga1-xInxNyAs1-y-zSbz subcells can exhibit an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.03 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.13 eV, measured at a junction temperature of 25° C.
In certain embodiments, a Ga1-xInxNyAs1-y-zSbz subcell can have values for x, y, and z of 0.068≤x≤0.078, 0.010≤y≤0.017, and 0.011≤z≤0.004; a band gap within the range from 1.15 eV to 1.16 eV; a short circuit current density Jsc greater than 9 mA/cm2; and an open circuit voltage Voc greater than 0.5 V. In such embodiments, the Ga1-xInxNyAs1-y-zSbz subcells can exhibit an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.21 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.30 eV, measured at a junction temperature of 25° C.
In certain embodiments, a Ga1-xInxNyAs1-y-zSbz subcell can have values for x, y, and z of 0.011≤x≤0.015, 0.04≤y≤0.06, and 0.016≤z≤0.020; a band gap within the range from 1.14 eV to 1.18 eV; a short circuit current density Jsc greater than 6 mA/cm2; and an open circuit voltage Voc greater than 0.5 V. In such embodiments, the Ga1-xInxNyAs1-y-zSbz subcells can exhibit an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.21 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.30 eV, measured at a junction temperature of 25° C.
In certain embodiments, a Ga1-xInxNyAs1-y-zSbz subcell can have values for x, y, and z of 0.012≤x≤0.016, 0.033≤y≤0.037, and 0.016≤z≤0.020; a band gap within the range from 1.18 eV to 1.22 eV; a short circuit current density Jsc greater than 6 mA/cm2; and an open circuit voltage Voc greater than 0.5 V. In such embodiments, the Ga1-xInxNyAs1-y-zSbz subcells can exhibit an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.24 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.30 eV, measured at a junction temperature of 25° C.
In certain embodiments, a Ga1-xInxNyAs1-y-zSbz subcell can have values for x, y, and z of 0.026≤x≤0.030, 0.024≤y≤0.018, and 0.005≤z≤0.009; a band gap within the range from 1.18 eV to 1.22 eV. In such embodiments, the Ga1-xInxNyAs1-y-zSbz subcells can exhibit an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.24 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.30 eV, measured at a junction temperature of 25° C.
In certain embodiments, a Ga1-xInxNyAs1-y-zSbz subcell can have values for x, y, and z wherein 0.075≤x≤0.082, 0.016≤y≤0.019, and 0.004≤z≤0.010, and the subcell can be characterized by a band gap within the range from 1.12 eV to 1.16 eV; a short circuit current density Jsc of at least 9.5 mA/cm2; and an open circuit voltage Voc of at least 0.40 V, wherein the Jsc and the Voc are measured using a 1 sun AM1.5D spectrum at a junction temperature of 25° C. In such embodiments, the Ga1-xInxNyAs1-y-zSbz subcells can exhibit an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.24 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.30 eV, measured at a junction temperature of 25° C.
In certain embodiments, a Ga1-xInxNyAs1-y-zSbz subcell can have values for x, y, and z wherein 0.011≤x≤0.016, 0.02≤y≤0.065, and 0.016≤z≤0.020, and the subcell can be characterized by a band gap within the range from 1.14 eV to 1.22 eV; a short circuit current density Jsc of at least 6 mA/cm2; and an open circuit voltage Voc of at least 0.50 V, wherein the Jsc and the Voc are measured using a 1 sun AM1.5D spectrum at a junction temperature of 25° C. In such embodiments, the Ga1-xInxNyAs1-y-zSbz subcells can exhibit an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.27 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.34 eV, measured at a junction temperature of 25° C.
In certain embodiments, a Ga1-xInxNyAs1-y-zSbz subcell can have values for x, y, and z wherein 0.016≤x≤0.0.024, 0.077≤y≤0.085, and 0.010≤z≤0.016, and the subcell can be characterized by a band gap within the range from 1.118 eV to 1.122 eV; a short circuit current density Jsc of at least 9 mA/cm2; and an open circuit voltage Voc of at least 0.40 V, wherein the Jsc and the Voc are measured using a 1 sun AM1.5D spectrum at a junction temperature of 25° C. In such embodiments, the Ga1-xInxNyAs1-y-zSbz subcells can exhibit an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.21 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.30 eV, measured at a junction temperature of 25° C.
In certain embodiments, a Ga1-xInxNyAs1-y-zSbz subcell can be characterized by a band gap within the range from 0.8 eV to 1.3 eV; and values for x, y, and z of 0.03≤x≤0.19, 0.008≤y≤0.055, and 0.001≤z≤0.05.
In certain embodiments, a Ga1-xInxNyAs1-y-zSbz subcell can have 0.06≤x≤0.09, 0.01≤y≤0.025, and 0.004≤z≤0.014, and the subcell can be characterized by, a band gap within the range from 1.12 eV to 1.16 eV; a short circuit current density Jsc equal to or greater than 9.5 mA/cm2; and an open circuit voltage Voc equal to or greater than 0.40 V, wherein the Jsc and the Voc are measured using a 1 sun AM1.5D spectrum at a junction temperature of 25° C. In such embodiments, the Ga1-xInxNyAs1-y-zSbz subcells can exhibit an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.21 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.30 eV, measured at a junction temperature of 25° C.
In certain embodiments, a Ga1-xInxNyAs1-y-zSbz subcell can have values of 0.004≤x≤0.08, 0.008≤y≤0.02, and 0.004≤z≤0.014, and the subcell can be characterized by, a band gap within the range from 1.14 eV to 1.22 eV; a short circuit current density Jsc equal to or greater than 6 mA/cm2; and an open circuit voltage Voc equal to or greater than 0.50 V, wherein the Jsc and the Voc are measured using a 1 sun AM1.5D spectrum at a junction temperature of 25° C. In such embodiments, the Ga1-xInxNyAs1-y-zSbz subcells can exhibit an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.27 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.30 eV, measured at a junction temperature of 25° C.
In certain embodiments, a Ga1-xInxNyAs1-y-zSbz subcell can have values of 0.06≤x≤0.09, 0.01≤y≤0.03, and 0.004≤z≤0.014, and the subcell can be characterized by, a band gap within the range from 1.118 eV to 1.122 eV; a short circuit current density Jsc equal to or greater than 9 mA/cm2; and an open circuit voltage Voc equal to or greater than 0.40 V, wherein the Jsc and the Voc are measured using a 1 sun AM1.5D spectrum at a junction temperature of 25° C. In such embodiments, the Ga1-xInxNyAs1-y-zSbz subcells can exhibit an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.21 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.30 eV, measured at a junction temperature of 25° C.
Multijunction photovoltaic cells provided by the present disclosure can comprise at least one subcell comprising a Ga1-xInxNyAs1-y-zSbz semiconductor material or subcell provided by the present disclosure, and wherein each of the subcells is lattice matched to each of the other subcells. Such multijunction photovoltaic cells can comprise three junctions, four junctions, five junctions, or six junctions, in which at least one of the junctions or subcells comprises a Ga1-xInxNyAs1-y-zSbz semiconductor material provided by the present disclosure. In certain embodiments, a multijunction photovoltaic cell comprises one subcell comprising a Ga1-xInxNyAs1-y-zSbz semiconductor material provided by the present disclosure, and in certain embodiments, two subcells comprising a Ga1-xInxNyAs1-y-zSbz semiconductor material provided by the present disclosure. The Ga1-xInxNyAs1-y-zSbz semiconductor material can be selected to have a suitable band gap depending at least in part on the structure of the multijunction photovoltaic cell. The band gap of the Ga1-xInxNyAs1-y-zSbz semiconductor material can be, for example, within the range from about 0.80 eV to about 0.14 eV.
Three junction photovoltaic cells having a bottom Ga1-xInxNyAs1-y-zSbz subcell (J3), a second (Al,In)GaAs subcell (J2), and a top InGaP or AlInGaP subcell (J1) were fabricated. Each of the subcells is lattice matched to (Al,In)GaAs. Therefore, each of the subcells is lattice matched to each of the other subcells. The parameters for the three junction photovoltaic cells measured using a 1 sun (1,366 W/m2) AM0 spectrum at 25° C. are provided in Table 5. Examples of measurements made on three junction cells are shown in
The three junction photovoltaic cells using a bottom Ga1-xInxNyAs1-y-zSbz subcell (J3) exhibit a high Voc of about 2.9 V, a high Jsc of about 16 mA/cm2, a high fill factor of about 85%, and a high efficiency of around 30%, illuminated with an AM0 spectrum. (Al)InGaP/(Al,In)GaAs/GaInNAsSb photovoltaic cells are characterized by an open circuit voltage Voc of at least 2.8 V, a short circuit current density of at least 17 mA, a fill factor of at least 80%, and an efficiency of at least 28%, measured using a 1 sun AM0 spectrum at a junction temperature of 25°.
(Al)InGaP/(Al,In)GaAs/GaInNAsSb photovoltaic cells are characterized by an open circuit voltage Voc from 2.8 V to 2.9 V, a short circuit current density from 16 mA/cm2 to 18 mA/cm2, a fill factor from 80% to 90% and an efficiency from 28% to 34%, illuminated with an AM0 spectrum.
(Al)InGaP/(Al,In)GaAs/GaInNAsSb photovoltaic cells are characterized by an open circuit voltage Voc from 2.85 V to 2.95 V, a short circuit current density from 15 mA/cm2 to 17 mA/cm2, a fill factor from 80% to 89% and an efficiency from 25% to 35%, measured using a 1 sun AM0 spectrum at a junction temperature of 25° C.
In certain embodiments, a three junction multijunction photovoltaic cell can comprise: a Ga1-xInxNyAs1-y-zSbz subcell characterized by a band gap from 0.9 eV to 1.1 eV; an (Al,In)GaAs subcell overlying the Ga1-xInxNyAs1-y-zSbz subcell, wherein the (Al,In)GaAs subcell is characterized by a band gap within the range from 1.3 eV to 1.5 eV; and an (Al)InGaP subcell overlying the (Al,In)GaAs subcell, wherein the (Al)InGaP subcell is characterized by a band gap within the range from 1.8 eV to 2.10 eV; wherein, each of the subcells is lattice matched to each of the other subcells; and the multijunction photovoltaic cell can be characterized by, an open circuit voltage Voc equal to or greater than 2.5 V; a short circuit current density Jsc equal to or greater than 12 mA/cm2; a fill factor equal to or greater than 75%; and an efficiency of at least 28%, measured using a 1 sun AM1.5D or AM0 spectrum at a junction temperature of 25° C.
In certain embodiments, a three junction multijunction photovoltaic cell can be characterized by, an open circuit voltage Voc within the range from 2.5 V to 3.2 V; a short circuit current density Jsc within the range from 15 mA/cm2 to 17.9 mA/cm2; a fill factor within the range from 80% to 90%; and an efficiency within the range from 28% to 33%, measured using a 1 sun AM0 spectrum at a junction temperature of 25° C.
In certain embodiments, a three junction multijunction photovoltaic cell can be characterized by, an open circuit voltage Voc within the range from 2.55 V to 2.85 V; a short circuit current density Jsc within the range from 13.0 mA/cm2 to 15 mA/cm2; a fill factor within the range from 75% to 87%; and an efficiency within the range from 28% to 35%, measured using a 1 sun AM1.5 D spectrum at a junction temperature of 25° C.
In certain embodiments, a multijunction photovoltaic cell can comprise: a Ga1-xInxNyAs1-y-zSbz subcell characterized by a band gap within the range from 0.9 eV to 1.05 eV; a (Al,In)GaAs subcell overlying the Ga1-xInxNyAs1-y-zSbz subcell, wherein the (Al,In)GaAs subcell is characterized by a band gap within the range from 1.3 eV to 1.5 eV; and an (Al)InGaP subcell overlying the (Al,In)GaAs subcell, wherein the (Al)InGaP subcell is characterized by a band gap within the range from 1.85 eV to 2.05 eV; wherein, each of the subcells is lattice matched to each of the other subcells; and the multijunction photovoltaic cell can be characterized by, an open circuit voltage Voc equal to or greater than 2.5 V; a short circuit current density Jsc equal to or greater than 15 mA/cm2; a fill factor equal to or greater than 80%; and an efficiency equal to or greater than 28%, measured using a 1 sun AM1.5D spectrum at a junction temperature of 25° C.
In certain embodiments, a three junction multijunction photovoltaic cell can be characterized by, an open circuit voltage Voc within the range from 2.6 V to 3.2 V; a short circuit current density Jsc within the range from 15.5 mA/cm2 to 16.9 mA/cm2; a fill factor within the range from 81% to 91%; and an efficiency within the range from 28% to 32%, measured using a 1 sun AM0 spectrum at a junction temperature of 25° C.
In certain embodiments a four junction photovoltaic cell can have the general structure as shown in
In certain four junction photovoltaic cells, the Ga1-xInxNyAs1-y-zSbz subcell (J3) can have a band gap within the range from 0.98 eV to 1.22 eV, from 0.98 eV to 1.20 eV, from 0.98 eV, to 0.18 eV, from 0.98 eV to 0.16 eV, from 0.98 eV to 0.14 eV, from 0.98 eV to 1.12 eV, from 0.99 eV to 1.11 eV, or within the range from 01.00 eV to 1.10 eV. The Ga1-xInxNyAs1-y-zSbz can be selected to substantially match the lattice constant of the (Si,Sn)Ge subcell and to provide a suitable band gap within a range, for example, within the range from 0.98 eV to 1.12 eV.
In certain embodiments of a four-junction photovoltaic cell, the Ga1-xInxNyAs1-y-zSbz subcell (J3) can have values for x, y, and z in which 0.075≤x≤0.083, 0.015≤y≤0.020, and 0.003≤z≤0.009.
In certain embodiments of a four-junction photovoltaic cell, the Ga1-xInxNyAs1-y-zSbz subcell (J3) can have values for x, y, and z in which 0.077≤x≤0.081, 0.0165≤y≤0.0185, and 0.004≤z≤0.009.
In certain embodiments of a four-junction photovoltaic cell, the Ga1-xInxNyAs1-y-zSbz subcell (J3) can have values for x, y, and z in which 0.078≤x≤0.080, 0.017≤y≤0.018, and 0.004≤z≤0.008.
In certain four junction photovoltaic cells the (Al,In)GaAs subcell (J2) can have a band gap within the range from 1.4 eV to 1.53 eV, from 1.42 eV to 1.51 eV, from 1.44 eV to 1.49 eV, or within the range from 1.46 eV to 1.48 eV.
The (Al,In)GaAs composition can be selected to match the lattice constant of the (Si,Sn)Ge subcell and to provide a suitable band gap with a range, for example, within the range from 1.4 eV to 1.53 eV.
In certain four junction photovoltaic cells the (Al)InGaP subcell (J1) can have a band gap within the range from 1.96 eV to 2.04 eV, from 1.97 eV to 2.03 eV, from 1.98 eV to 2.02 eV, or within the range from 1.99 eV to 2.01 eV. The (Al)InGaP composition is selected to match the lattice constant of the Ge subcell and to provide a suitable band gap within the range, for example, within the range within the range from 1.96 eV to 2.04 eV.
The composition of each of the subcells is selected to have an efficiency of at least 70% or at least 80% over a certain range of irradiance wavelengths or energies.
For example, a Ge subcell can exhibit an efficiency greater than 85% at irradiance energies within the range from about 0.77 eV to about 1.03 eV (about 1600 nm to 1200 nm), a Ga1-xInxNyAs1-y-zSbz subcell can exhibit an efficiency greater than 85% at irradiance energies within the range from 1.13 eV to 1.38 eV (1100 nm to 900 nm), a (Al,In)GaAs subcell can exhibit an efficiency greater than 90% at irradiance energies within the range from 1.51 eV to 2.00 eV (820 nm to 620 nm), and a (Al)InGaP subcell can exhibit an efficiency greater than 90% at irradiance energies within the range from 2.07 eV to 3.10 (600 nm to 400 nm).
Certain properties of four junction (Si,Sn)Ge/GaInNAsSb/(Al,In)GaAs/(Al)InGaP photovoltaic cells are shown in
Various properties of the four junction (Si,Sn)Ge/GaInNAsSb/(Al,In)GaAs/(Al)InGaP photovoltaic cells shown in
In certain embodiments, a multijunction photovoltaic cell can comprise: a first subcell comprising (Al)InGaP; a second subcell comprising (Al,In)GaAs underlying the first subcell; a third subcell comprising Ga1-xInxNyAs1-y-zSbz underlying the second subcell; and a fourth subcell comprising (Si,Sn)Ge underlying the third subcell; wherein, each of the subcells is lattice matched to each of the other subcells; the third subcell is characterized by a band gap from 0.83 eV to 1.22 eV; and the third subcell is characterized by an efficiency greater than 70% at an irradiance energy throughout the range from 0.95 eV to 1.55 eV at a junction temperature of 25° C.
In certain embodiments, a multijunction photovoltaic cell can comprise Ga1-xInxNyAs1-y-zSbz subcell characterized by an efficiency greater than 80% at an irradiance energy throughout the range from 1.1 eV to 1.5 eV.
In certain embodiments, a four-junction multijunction photovoltaic cell comprising a Ga1-xInxNyAs1-y-zSbz subcell can be characterized by, an open circuit voltage Voc equal to or greater than 2.5 V; a short circuit current density Jsc equal to or greater than 8 mA/cm2; a fill factor equal to or greater than 75%; and an efficiency greater than 25%, measured using a 1 sun AM1.5D or AM0 spectrum at a junction temperature of 25° C.
In certain embodiments, a four-junction multijunction photovoltaic cell comprising a Ga1-xInxNyAs1-y-zSbz subcell can be characterized by, an open circuit voltage Voc equal to or greater than 3.0 V; a short circuit current density Jsc equal to or greater than 15 mA/cm2; a fill factor equal to or greater than 80%; and an efficiency greater than 25%, measured using a 1 sun AM1.5D or AM0 spectrum at a junction temperature of 25° C.
In certain embodiments, a four-junction multijunction photovoltaic cell comprising a Ga1-xInxNyAs1-y-zSbz subcell can be characterized by, an open circuit voltage Voc from 2.5 V to 3.5 V; a short circuit current density Jsc from 13 mA/cm2 to 17 mA/cm2; a fill factor from 80% to 90%; and an efficiency from 28% to 36%, measured using a 1 sun AM0 spectrum at a junction temperature of 25° C.
In certain embodiments, a four-junction multijunction photovoltaic cell comprising a Ga1-xInxNyAs1-y-zSbz subcell can be characterized by, an open circuit voltage Voc from 3.0 V to 3.5 V; a short circuit current density Jsc from 8 mA/cm2 to 14 mA/cm2; a fill factor from 80% to 90%; and an efficiency from 28% to 36%, measured using a 1 sun AM1.5D spectrum at a junction temperature of 25° C.
In certain embodiments, a four-junction multijunction photovoltaic cell comprising a Ga1-xInxNyAs1-y-zSbz subcell can comprise: a first subcell having a band gap from 1.9 eV to 2.2 eV; a second subcell having a band gap from 1.40 eV to 1.57 eV; a third subcell having a band gap from 0.98 eV to 1.2 eV; and a fourth subcell having a band gap from 0.67 eV.
In certain embodiments of a four-junction multijunction photovoltaic cell comprising a Ga1-xInxNyAs1-y-zSbz subcell values for x, y, and z are 0.075≤x≤0.083, 0.015≤y≤0.020, and 0.003≤z≤0.09.
In certain embodiments of a four-junction multijunction photovoltaic cell comprising a Ga1-xInxNyAs1-y-zSbz subcell, the Ga1-xInxNyAs1-y-zSbz subcell can be characterized by, an open circuit voltage Voc from 0.42 V to 0.57 V; a short circuit current density Jsc from 10 mA/cm2 to 13 mA/cm2; and a band gap from 1.0 eV to 1.17 eV, measured using a 1 sun AM1.5D spectrum at a junction temperature of 25° C.
To increase the photovoltaic cell efficiency, five junction photovoltaic cells can be fabricated. Examples of the composition of photovoltaic cell stacks for three junction, four junction, and five junction photovoltaic cells are shown in
To demonstrate the feasibility of using adjacent Ga1-xInxNyAs1-y-zSbz subcells, four junction photovoltaic cells having a bottom Ga1-xInxNyAs1-y-zSbz subcell and an overlying Ga1-xInxNyAs1-y-zSbz subcell were fabricated and evaluated. The four junction photovoltaic cells were fabricated on a GaAs substrate. Each of the subcells is substantially lattice matched to each of the other subcells and to the GaAs substrate. The multijunction photovoltaic cells do not comprise a metamorphic buffer layer between adjacent subcells. The composition of each of the two Ga1-xInxNyAs1-y-zSbz subcells, the (Al,In)GaAs subcell, and the (Al)InGaP subcell is selected to lattice match to the GaAs substrate and to provide an appropriate band gap.
The four junction photovoltaic cells had a bottom Ga1-xInxNyAs1-y-zSbz subcell (J4), an overlying Ga1-xInxNyAs1-y-zSbz subcell (J3), an overlying (Al,In)GaAs subcell (J2), and a top (Al)InGaP subcell (J1). The band gaps and Jsc under a 1 sun AM1.5D or AM0 spectrum are shown in Table 7.
The internal and external quantum efficiencies for each of the subcells of the photovoltaic cell presented in Table 6 is shown in
The four junction photovoltaic cells having two Ga1-xInxNyAs1-y-zSbz subcells exhibit internal and external quantum efficiencies over 70% throughout an irradiance wavelength range from about 400 nm (3.1 eV) to about 1300 nm (0.95 eV), and over 80% throughout an irradiance wavelength range from about 450 nm (2.75 eV) to about 1200 nm (1.03 eV).
Other four junction photovoltaic cells having two Ga1-xInxNyAs1-y-zSbz similar to those presented in Table 7 exhibit an open circuit voltage from about 3.67 eV to about 3.69 eV, a short circuit current density from about 9.70 mA/cm2 to about 9.95 mA/cm2, a fill factor from about 80% to about 85% and an external quantum efficiency from about 29.0% to about 31% measured using a 1 sun AM) or AM1.5D spectrum at a junction temperature of 25° C.
In these photovoltaic cells, the bottom Ga1-xInxNyAs1-y-zSbz subcell (J4) has a band gap from 0.95 eV to about 0.99 eV such as from 0.96 eV to 0.97 eV, and values for x, y, and z of 0.11≤x≤0.15, 0.030≤y≤0.034 and 0.007≤z≤0.14, and in certain embodiments, values for x, y, and z of 0.12≤x≤0.14, 0.031≤y≤0.033 and 0.007≤z≤0.14. In such embodiments, the Ga1-xInxNyAs1-y-zSbz subcells can exhibit an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.03 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.15 eV, measured at a junction temperature of 25° C.
In these photovoltaic cells, the second Ga1-xInxNyAs1-y-zSbz subcell (J3) has a band gap from 1.1 eV to about 1.3 eV, and values for x, y, and z of 0.026≤x≤0.030, 0.014≤y≤0.018 and 0.005≤z≤0.009, and in certain embodiments, values for x, y, and z of 0.027≤x≤0.029, 0.015≤y≤0.017 and 0.006≤z≤0.008. In such embodiments, the Ga1-xInxNyAs1-y-zSbz subcells can exhibit an efficiency of at least 70% at an irradiance energy from 1.38 eV to 1.34 eV, and an efficiency of at least 80% at an irradiance energy from 1.38 eV to 1.34 eV, measured at a junction temperature of 25° C.
These results demonstrate the feasibility of incorporating two Ga1-xInxNyAs1-y-zSbz subcells into a photovoltaic cell to improve multijunction photovoltaic cell performance. As shown in
A four-junction photovoltaic cell comprising two Ga1-xInxNyAs1-y-zSbz subcells can be adapted for use in five junction multijunction photovoltaic cells. The stack of (Al)InGaP/(Al,In)GaAs/Ga1-xInxNyAs1-y-zSbz/Ga1-xInxNyAs1-y-zSbz layers can overlies a Ge layer that can function as the fifth subcell. In photovoltaic cells having a Ge subcell, each of the base layers can be lattice matched to the Ge subcell.
In certain embodiments, a four- and five junction multijunction photovoltaic cell comprising two Ga1-xInxNyAs1-y-zSbz subcells can comprise: a first subcell comprising (Al)InGaP; a second subcell comprising (Al,In)GaAs underlying the first subcell; a third subcell comprising Ga1-xInxNyAs1-y-zSbz underlying the second subcell; and a fourth subcell comprising Ga1-xInxNyAs1-y-zSbz underlying the third subcell; wherein, each of the subcells is lattice matched to each of the other subcells; each of the fourth subcell and the third subcell is characterized by a band gap with a range from 0.83 eV to 1.3 eV; and each of the fourth subcell and the third subcell is characterized by an efficiency greater than 70% at an irradiance energy throughout the range from 0.95 eV to 1.55 eV.
In certain embodiments, a four- and five junction multijunction photovoltaic cell comprising two Ga1-xInxNyAs1-y-zSbz subcells, each of the two Ga1-xInxNyAs1-y-zSbz subcells can be characterized by an efficiency greater than 80% at an irradiance energy throughout the range from 1.1 eV to 1.5 eV.
In certain embodiments, a four- and five junction multijunction photovoltaic cell comprising two Ga1-xInxNyAs1-y-zSbz subcells, the multijunction photovoltaic cell can be characterized by, an open circuit voltage Voc equal to or greater than 2.8 V; a short circuit current density Jsc equal to or greater than 18 mA/cm2; a fill factor equal to or greater than 80%; and an efficiency equal to or greater than 29%, measured using a 1 sun 1.5 AM0 spectrum at a junction temperature of 25° C.
In certain embodiments, a four- and five junction multijunction photovoltaic cell comprising two Ga1-xInxNyAs1-y-zSbz subcells, the multijunction photovoltaic cell can comprise: a first subcell characterized by a band gap from 1.90 eV to 2.20 eV; a second subcell characterized by a band gap from 1.4 eV to 1.7 eV; a third subcell characterized by a band gap from 0.97 eV to 1.3 eV; and a fourth subcell characterized by a band gap from 0.8 eV to 1 eV.
In certain embodiments, a four- and five junction multijunction photovoltaic cell comprising two Ga1-xInxNyAs1-y-zSbz subcells, the multijunction photovoltaic cell can comprise: a fourth subcell comprising Ga1-xInxNyAs1-y-zSbz is characterized by a band gap from 0.9 eV to 1 eV; a third subcell comprising Ga1-xInxNyAs1-y-zSbz is characterized by a band gap from 1.1 eV to 1.3 eV; a second subcell comprising (Al,In)GaAs is characterized by a band gap from 1.5 eV to 1.7 eV; and a first subcell comprising (Al)InGaP is characterized by a band gap from 1.9 eV to 2.1 eV; wherein the multijunction photovoltaic cell can be characterized by, an open circuit voltage Voc equal to or greater than 3.5 V; a short circuit current density Jsc equal to or greater than 8 mA/cm2; a fill factor equal to or greater than 75%; and an efficiency equal to or greater than 27%, measured using a 1 sun AM1.5D spectrum at a junction temperature of 25° C.
In certain embodiments, a four- and five junction multijunction photovoltaic cell comprising two Ga1-xInxNyAs1-y-zSbz subcells, the multijunction photovoltaic cell can be characterized by, an open circuit voltage Voc from 3.65 V to 3.71 V; a short circuit current density Jsc from 9.7 mA/cm2 to 10.0 mA/cm2; a fill factor from 80% to 85%; and an efficiency from 29% to 31%, measured using a 1 sun AM1.5D spectrum at a junction temperature of 25° C.
In certain embodiments, a four- and five junction multijunction photovoltaic cell comprising two Ga1-xInxNyAs1-y-zSbz subcells, the multijunction photovoltaic cell can be characterized by, an open circuit voltage Voc equal to or greater than 2.5 V; a short circuit current density Jsc equal to or greater than 8 mA/cm2; a fill factor equal to or greater than 75%; and an efficiency equal to or greater than 25%, measured using a 1 sun AM1.5D or AM0 spectrum at a junction temperature of 25° C.
In certain embodiments, a four- and five junction multijunction photovoltaic cell comprising two Ga1-xInxNyAs1-y-zSbz subcells, the multijunction photovoltaic cell can be characterized by, an open circuit voltage Voc from 2.5 V to 3.5 V; a short circuit current density Jsc from 13 mA/cm2 to 17 mA/cm2; and a fill factor from 80% to 90%; and an efficiency from 28% to 36%, measured using a 1 sun AM0 spectrum at a junction temperature of 25° C.
In certain embodiments, a four- and five junction multijunction photovoltaic cell comprising two Ga1-xInxNyAs1-y-zSbz subcells, the multijunction photovoltaic cell can be characterized by, an open circuit voltage Voc from 3 V to 3.5 V; a short circuit current density Jsc from 8 mA/cm2 to 14 mA/cm2; a fill factor from 80% to 90%; and an efficiency from 28% to 36%, measured using a 1 sun AM1.5D spectrum at a junction temperature of 25° C.
Five junction multijunction photovoltaic cells are also provided. A five junction multijunction photovoltaic cell an comprise two Ga1-xInxNyAs1-y-zSbz subcells. The two Ga1-xInxNyAs1-y-zSbz subcells can overlies a (Si,Sn)Ge subcell and can be lattice matched to the (Si,Sn)Ge subcell. Each of the subcells can be lattice matched to each of the other subcells and can be lattice matched to the (Si,Sn)Ge subcell. A (Si,Sn)Ge subcell can have a band gap with a range from 0.67 eV to 1.0 eV.
In certain embodiments, a five junction multijunction photovoltaic cell comprising two Ga1-xInxNyAs1-y-zSbz subcells can comprise: a first subcell comprising (Al)InGaP; a second subcell comprising (Al,In)GaAs underlying the first subcell; a third subcell comprising Ga1-xInxNyAs1-y-zSbz underlying the second subcell; a fourth subcell comprising Ga1-xInxNyAs1-y-zSbz underlying the third subcell; a fifth subcell comprising (Si,Sn)Ge underling the fourth subcell; wherein, each of the subcells is lattice matched to each of the other subcells; each of the fourth subcell and the third subcell is characterized by a band gap with a range from 0.83 eV to 1.3 eV; and each of the fourth subcell and the third subcell is characterized by an efficiency greater than 70% at an irradiance energy throughout the range from 0.95 eV to 1.55 eV.
In certain embodiments of a five junction multijunction photovoltaic cell each of the two Ga1-xInxNyAs1-y-zSbz subcells can be characterized by an efficiency greater than 80% at an illumination energy throughout the range from 1.1 eV to 1.5 eV.
In multijunction photovoltaic cells provided by the present disclosure, one or more subcells can comprise AlInGaAsP where the content each Group III and each Group V element can range from 0 to 1, and the AlInGaAsP base can be lattice matched to a substrate and to each of the other subcells in the multijunction photovoltaic cell. The band gap of an AlInGaAsP subcell can be from 1.8 eV to 2.3 eV. An AlInGaAsP subcell can comprise an (Al)InGaP subcell or an (Al,In)GaAs subcell. Multijunction photovoltaic cells provided by the present disclosure can comprise at least one Ga1-xInxNyAs1-y-zSbz and one or more of the other subcells can comprise an AlInGaAsP subcell.
In certain embodiments of multijunction photovoltaic cells, a subcell such as a Ga1-xInxNyAs1-y-zSbz and/or an AlInGaAsP subcell can be a homojunction in which the emitter and the base of a subcell comprise the same material composition and have the same band gap.
In certain embodiments of multijunction photovoltaic cells, a subcell such as a Ga1-xInxNyAs1-y-zSbz and/or an AlInGaAsP subcell can be a heterojunction in which the emitter and the base of a subcell comprise the same material but have a different composition such that the band gap of the emitter and the band gap of the base of a subcell are different. In certain embodiments, the band gap of the emitter is higher than the band gap of the base, and in certain embodiments, the band gap of the emitter is lower than the band gap of the base. Reverse heterojunction Ga1-xInxNyAs1-y-zSbz subcells are disclosed in U.S. Pat. No. 9,153,724, which is incorporated by reference in its entirety.
It should be noted that the embodiments specified above have specific profiles for doping that result in the creation of specific electric fields within the base and/or emitter of a dilute nitride solar cell. These examples are specified for illustration purposes and one skilled in the art can vary the doping profile in many other ways and configurations to achieve particular results. Recitation of these specific embodiments is not intended to limit the invention, which is set forth fully in the claims.
This application is a continuation-in-part of U.S. application Ser. No. 14/935,145 filed on Nov. 6, 2015, now allowed, which is a continuation of U.S. application Ser. No. 12/914,710 filed on Oct. 28, 2010, issued as U.S. Pat. No. 9,214,580; and this application is a continuation-in-part of U.S. application Ser. No. 15/595,391 filed on May 15, 2017, which claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Application No. 62/340,294 filed on May 23, 2016, each of which is incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62340294 | May 2016 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12914710 | Oct 2010 | US |
| Child | 14935145 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14935145 | Nov 2015 | US |
| Child | 16431521 | US | |
| Parent | 15595391 | May 2017 | US |
| Child | 12914710 | US |
