Patent Application
20210104908
The present invention relates to the incorporation of high band gap solar cells into screens of mobile electronic devices such as smartphones.
Currently, most mobile electronic devices have to be recharged via connection to an electrical grid. Current smartphones' batteries are capable of powering up to 5000 mAh of charge, with a voltage of 3.7 V for lithium-ion batteries with graphite anodes, which supplies a total energy of 18.5 Wh. Such energy supply, for the regular practice of most users, is sufficient for a day or two. Additional operation time may be very valuable to the owner once the battery is fully discharged, when a conventional charging mechanism is not available. Extra-charging may be proved invaluable during emergency as well.
It should be noted that the spectral sensitivity of human visual perception of brightness decreases substantially towards the short wavelengths of the visible spectrum, especially under 450 nm. Nonetheless, the solar irradiance spectrum, even after being filtered by the atmosphere, maintains a power density illumination of ca. 4.7 mW/cm2 of light under the wavelength of 400 nm. Similarly, the solar flux is ca. 10.9 mW/cm2 of light under the wavelength of 450 nm, ca. 15.6 mW/cm2 of light under the wavelength of 480 nm and ca. 18.7 mW/cm2 of light under the wavelength of 500 nm (all integrated from AM1.5 G standard). It should also be noted that an extraction of even a few percent of these energy fluxes by the screen area would be a considerable source for recharging mobile devices such as cellular phones. In addition, it should be noted that glass and most conductive transparent materials usually have significant absorbance under the wavelength of about 350 nm. The power flux up to 350 nm is only ca. 1.4 mW/cm2.
The incorporation of conventional solar panels into the back of mobile instruments, is a straightforward approach and was discussed in few prior art cases. Nonetheless, additional costs, additional weight and design issues, hinder the idea from manifesting into practical use. Additional prior art (as in: Chen, C. US 2011/0157034 A1), considered the utilization of conventional solar panels situated on the screen, between the light source of the screen and the observer. Solar cells such as silicon-based solar cells, which possess a low band gap of 1.14 eV, absorb light throughout the visible spectrum. Even a very thin layer of silicon, which absorbs only part of the light, would require an appropriate adjustment to the increase in projected light intensity. It should be noted that the screens of mobile devices are a major power-consuming component (Carroll, A. et al. USENIX annual technical conference. 14, (2010)). Since the power conversion efficiency of solar panels is limited to practical use of about 20%, significant energetic loss is expected when the screen is not under full sun irradiation conditions.
It is therefore an object of the current invention to disclose a method to incorporate a high energy photon harvesting photovoltaic apparatus into cellular phone screens. Such solar cell is designed to be situated on top of the main light emitting layers of the screen and collect low wavelength UV and violet-blue light. Using this configuration, it will be possible to collect high-energy photons from sun radiation for the production of direct current, and the recharging of the batteries. Additionally, similar light, emitted from the screen itself, will be absorbed by the active layer of the solar cell as well, with minimum effect on the screen display properties. Another benefit of the current invention is the protection of the screen from sun damage through the collection of UV light on top of the screen, before it reaches the inner layers of the screen. Yet another benefit of the current design is the lightweight and low cost properties of the photovoltaic apparatus, intended for incorporation into the screen itself. In this case, the screen serves as a rigid substrate for the thin layers of the solar cell's constituents.
The incorporated solar cells consist of thin layers with different functionalities, which can be a part of the device's screen itself. Another key element of the solar cell is the low absorbance properties, of all of its layers, in the visible wavelengths above 500 nm and relatively high absorbance in the spectral region below wavelengths of 500 nm, preferably including high absorbance in the UVA (315-400 nm) and UVB (280-315 nm) regions. The family of high band gap solar cells includes three types of cells, using three different active materials. high band gap semiconducting materials, quantum dots and organic solar cells i.e. organic photovoltaics. Two additional transparent conductive layers will be applied as cathodic and anodic contacts, along with additional layers that promote the directionality of the current, such as electron/hole transport layers.
According to the current invention, the solar cell will be located below the top layer of the screen. For example, in LCD (liquid-crystal display) screens, the twisted nematic liquid crystal layer is usually located between two conductive transparent electrodes and two layers of polarizing filters. The top layer of the screen is usually transparent and conductive, as part of the touchscreen functionality. The solar cell will be situated further out from the liquid crystal layer, or the layers of another display method, towards the top surface of the screen. This configuration will be applied to all LCD technologies, such as: TN (twisted nematic), VA (vertical alignment), PVA (patterned vertical alignment) IPS (in plane switching), in addition to displays of different illumination methods such as QLED (quantum-dot light-emitting diode), MicroLED, AMOLED (active-matrix organic light-emitting diode) and related technologies as well. Similarly, OLED (organic light-emitting diode) screens are constructed with equivalent transparent and conductive layers on both sides of the organic material, as well as transparent layer on the top surface of the screen. The solar cell layers will be located between the organic material layer and the top surface. The conductive layers of the solar cells will be composed of transparent conductive materials such as: ITO (indium tin oxide), FTO (fluorine tin oxide), aluminum, gallium or indium-doped zinc oxide (AZO, GZO or IZO), conductive polymers such as PEDOT:PSS i.e. poly(3,4-ethylenedioxythiophene) polystyrene sulfonate, graphene and carbon nanotubes.
Inorganic semiconductor based solar cells will operate, according to the current invention, with a large band gap—over 2.48 eV which corresponds to 500 nm photon. In this way, visible light with wavelengths above 500 nm will be transmitted through the solar cell. Examples for such materials include, and are not limited to Cr2O3; MnO; CoO; TiO2; NiO; As2S3; ZnSe; ZnS; ZnO; Ge3N4; WO3; BCN; GaN; SrTiO3; C3N4; Bi2WO6 and SiC, including all polymorphs and blends with band gaps larger than 2.58 eV. The application of the materials can be done through chemical deposition methods such as chemical solution deposition, chemical bath deposition, spin coating, dip coting, CVD (chemical vapor deposition) ALD (atomic layer deposition), or physical deposition methods such as sputtering, pulsed laser deposition and others. Additional selective HTM (hole transport materials such as PEDOT: PSS and spiro group derivatives) or ETL (electron transport layers such as compact or mesoporous TiO2 layers) may be added (both or only one type) between the photoactive layer and the cathode/anode. These layers selectively allow only holes or electrons to pass through them and thus induce an anisotropic diffusion of charges under illumination. Quantum dots or nanorods composed of semiconducting materials may replace the bulk materials mentioned above. Due to the quantum size effect, it is possible to accurately tune a band gap to 2.58 eV or higher, and achieve the desired visible light absorbance. Thanks to this increase in band gap due to nano-confinement, it is possible to incorporate other semiconducting materials with smaller bulk band gaps as well as core-shell nanoparticles in order for the desired band gap to be achieved. Furthermore, the utilization of organic solar cell configuration is possible. While most light-absorbing donor molecules and polymers, traditionally used in organic solar cells, possess low band gaps (referring to the HOMO-LUMO difference), the use of high band gap substances is notable as well. For example, recent prior art (Garcias-Morales, C. et al. Molecules 22.10 (2017): 1607) demonstrated a bulk heterojunction organic solar cell which employs a donor of thieno[3,4-c]pyrrole-4,6-dione derivative and [6,6]-phenyl C71 butyric acid methyl ester (PC71BM) acceptor. A maximal absorbance at a wavelength of 433 nm and a band gap of 2.48 eV, equivalent to almost 500 nm wavelength light, were observed together with 2.32±0.28 power conversion efficiency. Thereby, the employment of light absorbing acceptor molecules and polymers in this invention is limited to substances with band gaps larger than 2.48 eV. Any tandem multi-junction combination of the previously mentioned solar cells is conceivable for the purpose of higher total power conversion efficiency.
It is a core purpose of the current invention to disclose a method to incorporate a high energy photon harvesting photovoltaic apparatus into mobile electronic devices such as smartphones; laptop computers; tablets; e-readers and mobile phones. These solar cells are incorporated into the screens of the devices, and are formulated according to the previously mentioned solar cell constructions. A key feature of the incorporated solar cells is substantial transparency in the visible wavelengths above 500 nm, which allow for regular functionality of the screen. The objective of this incorporation is to provide an alternative way to recharge the devices' batteries fully or partially.
Another object of the present invention is to provide a method to reduce UV light and high energy visible light emittance from the screens of cellular phones, tablets, and portable electronic devices which include a screen.
A specific example of the method is a smartphone comprising a screen which is composed of an LDC module assembly. On top of said assembly, a conductive ITO layer was deposited using CVD. A compact TiO2 layer of 30 nm, acting as an ETL was then applied using chemical bath deposition with TiCl4 solution. A photoactive silicon carbide (SiC) layer was later deposited by CVD method e.g. 200 nm thick layer. Using ALD, a conducive graphene layer was formed on top of the silicon carbide. Finally, conventional methods were applied to form the touch screen mechanism. Said anodic ITO layer and cathodic graphene layer are connected to the charging mechanism of the phone. The band gap of the SiC 6H(alpha) layer is about 3.05 eV and allows visible light above a wavelength of 407 nm to pass freely from the LCD assembly to the user. Photons under the wavelength of 407 nm will be absorbed by the solar cell at high percentage and generate power to recharge the battery of the smartphone.
More advantages, characteristics, features and operation methods of the current invention will emerge as a consequence of the following claims and the accompanying drawings. Similarly, the functionality of the parts and their combinations and elements of manufacture will be more noticeable as well. A brief description of the drawings appears next, and is followed by a detailed one and then the accompanying claims.
The believed key elements of the invention are provided below by way of example.
Substantial emphasis should be placed on the fact that the drawings are for illustration and clarification purposes only, and are not intended to be a definition of the limits of this invention.
Reference is now made to
| Number | Date | Country | |
|---|---|---|---|
| 62910471 | Oct 2019 | US |
