Patent Application
20130000713
This application claims priority to and the benefit of Korean Patent Application No. 10-2011-0063970 filed in the Korean Intellectual Property Office on Jun. 29, 2011, the entire contents of which are incorporated herein by reference.
(a) Field of the Invention
The present invention relates to a nanostructure, a manufacturing method thereof, and a solar cell including the same.
(b) Description of the Related Art
In general, a nanostructure has various functionalities in electrical, electronic, optical, and engineering applications such that research thereof has been actively performed as a core element in application fields such as energy, displays, sensors, and bionics.
Particularly, a metal oxide such as TiO2 and ZnO may have a shape of a nanoparticle, a nanowire, or a nanotube, and a nanostructure of a desired shape and structure for various applications may be formed as the importance of a technique for integrating a nanostructure of other shapes is increased. Particularly, the nanostructure is largely applied as a photoelectrode of a dye sensitized solar cell (DSSC).
The dye sensitized solar cell includes a conductive transparent electrode, a porous photoelectrode absorbed with a dye and made of titanium oxide (TiO2) nanoparticles, an electrolyte, and an opposite electrode, and the electrons inside the dye that are excited by visible rays are injected to the titanium oxide TiO2 of the porous photoelectrode and are moved. However, the porous photoelectrode made of titanium oxide (TiO2) has a poor depletion layer such that an energy loss due to hole and electron recombination generated while the electron is moved in the porous photoelectrode is increased, thereby decreasing energy conversion efficiency.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.
The present invention provides a nanostructure that increases solar cell energy conversion efficiency, a manufacturing method thereof, and a solar cell including the same.
A nanostructure according to an exemplary embodiment of the present invention includes: a plurality of nanowires formed at predetermined intervals on a substrate; a plurality of nanobranches enclosing side surfaces of the nanowires; and a plurality of sub-nanobranches enclosing side surfaces of the nanobranches.
The nanowires, the nanobranches, and the sub-nanobranches may include zinc oxide.
The nanowires may be formed in a direction perpendicular to the surface of the substrate.
The nanobranches may be formed by removing a polymer from the nanowires and by progressing a hydrothermal reaction, and the nanobranches are extended in the side direction of the nanowires.
The sub-nanobranches may be formed by repeating the hydrothermal reaction, and the sub-nanobranches are extended in the side direction of the nanobranches.
A manufacturing method of a nanostructure according to an exemplary embodiment of the present invention includes: adhering a plurality of first nanoparticles on a substrate to form a nanoseed layer; growing the nanoseed layer on the substrate to form a plurality of nanowires; adhering a plurality of second nanoparticles to the side surface of the nanowires to form a nanoshell layer; and growing the nanoshell layer to form a plurality of nanobranches.
The forming of the nanoseed layer may include filling a seed solution including a plurality of first nanoparticles into a seed container, and positioning a substrate inside the seed container to form the nanoseed layer on the substrate.
The forming of the nanowires may include soaking the substrate formed with the nanoseed layer in a precursor solution including the polymer, and progressing a hydrothermal reaction for the nanoseed layer.
A plurality of nanowires may be formed at predetermined intervals on the substrate.
The method may further include removing the polymer from the nanowires after forming a plurality of nanowires.
The nanowires may be heated to remove the polymer.
The nanobranches may be formed by growing the nanoshell layer in the side surface of the nanowires.
The method may further include progressing a hydrothermal reaction for the nanobranches to form a plurality of sub-nanobranches at the side surface of the nanobranches.
A solar cell according to an exemplary embodiment of the present invention includes: a photoelectrode made of a nanostructure including a plurality of nanowires formed at predetermined intervals on a substrate, a plurality of nanobranches enclosing the side surface of the nanowires, a plurality of sub-nanobranches enclosing the side surface of the nanobranches, and a dye absorbed to the photoelectrode; an opposite electrode facing the photoelectrode; and an electrolyte positioned between the photoelectrode and the opposite electrode.
The nanowires, the nanobranches, and the sub-nanobranches may include zinc oxide.
According to the present invention, a nanostructure includes a plurality of nanowires formed at predetermined intervals on a substrate and a plurality of nanobranches enclosing the side surface of the nanowires, thereby increasing the specific surface area for absorbing light, and resultantly the light absorption ratio may be improved.
Further, the dye sensitized solar cell having the photoelectrode including the nanostructure according to an exemplary embodiment of the present invention is manufactured such that the loss of electrons generated by light reaction is reduced, and thereby the energy conversion efficiency of the dye sensitized solar cell may be improved.
The nanostructure according to an exemplary embodiment of the present invention is applied to various electronic devices such as a photosensor and a display such that the performance thereof may be improved.
The present invention will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.
Descriptions of parts not related to the present invention are omitted, and like reference numerals designate like elements throughout the specification.
A nanostructure 300 according to an exemplary embodiment of the present invention will now be described with reference to
As shown in
The nanowires 310, the nanobranches 320, and the sub-nanobranches 330 are formed of zinc oxide (ZnO), and the nanowires 310 are formed in a direction perpendicular to a surface of the substrate 100. A plurality of nanowires 310 further include a polymer of hexamethylenetetramine (HMTA) and polyethylenimine (PEI), and the polymer interrupts the side growth of a nanoseed layer 31 and does not interrupt the axis direction growth of the nanoseed layer 31 when progressing a hydrothermal reaction such that a plurality of nanowires 310 are formed at the predetermined interval on the substrate 100.
The polymer is removed from a nanoshell layer 32 enclosing the nanowires 310 when progressing the hydrothermal reaction such that the side growth and the axis direction growth of the nanoshell layer 32 both progress. Accordingly, the nanobranches 320 are grown on all sides of a plurality of nanowires 310.
Also, the polymer is removed at the side surface of the grown nanobranches 320 such that the side growth and the axis direction growth of the nanoshell layer 33 remaining at the nanobranches 320 both progress. Accordingly, the sub-nanobranches 330 are grown on all sides of a plurality of nanobranches 320.
An entire surface area per unit mass or a unit volume of any particle is referred as a specific surface area, and as described above, the specific surface area of the nanostructure 300 is increased by the nanowires 310, the nanobranches 320, and the sub-nanobranches 330.
As described above, the nanostructure 300 according to an exemplary embodiment of the present invention is made of the nanowires 310, the nanobranches 320, and the sub-nanobranches 330 such that the specific surface area may be maximized, and thereby a dye deposition ratio and an absorption ratio may be improved, resultantly energy conversion efficiency may be improved.
A manufacturing method of a nanostructure 300 according to an exemplary embodiment of the present invention will be described with reference to
In a manufacturing method of a nanostructure 300 according to an exemplary embodiment of the present invention, as shown in
Also, the substrate 100 is positioned inside the seed container 50 to form the nanoseed layer 31 on the substrate 100. A plurality of first nanoparticles 1 are adhered to the substrate 100, thereby forming the nanoseed layer 31.
Next, as shown in
A hydrothermal reaction is progressed in the pressure container 70 for 3 to 7 hours at a temperature of 65 degrees to 95 degrees such that the nanoseed layer 31 is grown to form a plurality of nanowires 310.
The polymer of hexamethylenetetramine (HMTA) and polyethylenimine (PEI) formed on the surface of the substrate 100 interrupts the side growth of the nanoseed layer 31 and does not interrupt the axis direction (Y) growth of the nanoseed layer 31 such that a plurality of nanowires 310 are formed at a predetermined interval on the substrate 100.
The hydrothermal reaction is repeated such that a plurality of nanowires 310 may be grown in the direction perpendicular to the surface of the substrate 100.
Next, as shown in
For this, the substrate 100 is soaked in a seed solution in which a plurality of second nanoparticles 2 made of zinc oxide (ZnO) are dispersed in ethanol. Accordingly, the plurality of second nanoparticles enclose and are adhered to the side surface of the plurality of nanowires 310 to form the nanoshell layer 32.
Next, as shown in
The hydrothermal reaction is progressed at a temperature of 65 degrees to 95 degrees for 3 to 7 hours in the pressure container 70 such that the nanoshell layer 32 is grown in the side surface of the nanowires 310 to form a plurality of nanobranches 320.
The polymer is removed from the nanoshell layer 32 and the side growth and the axis direction growth of the nanoshell layer 32 are progressed such that the nanobranches 320 are grown on all side surfaces of a plurality of nanowires 310.
Also, the above hydrothermal reaction is repeated to grow a plurality of sub-nanobranches 330 in various directions on the side surface of the nanobranches 320 such that the specific surface area may be widened.
As shown in
d) is a SEM photo showing a side growth of nanobranches in a case that a polymer is not removed, and
As shown in
As described above, the manufacturing method of the nanostructure 300 according to an exemplary embodiment of the present invention forms the nanobranches 320 and the sub-nanobranches 330 after removing the polymer adhered to the nanowires 310 such that the nanobranches 320 and the sub-nanobranches 330 are grown larger.
Accordingly, the specific surface area may be maximally widened such that the dye deposition ratio and the light absorption ratio may be improved, and thereby the energy conversion efficiency may be improved.
As shown in
The nanostructure 300 includes a plurality of nanowires 310 formed at a predetermined interval on a substrate 100, a plurality of nanobranches 320 enclosing a side surface of the nanowires 310, and a plurality of sub-nanobranches 330 enclosing the side surface of the nanobranches 320.
The nanowires 310, the nanobranches 320, and the sub-nanobranches 330 are formed of zinc oxide (ZnO), and the nanowires 310 are formed in a direction perpendicular to a surface of the substrate 100. A plurality of nanowires 310 further include a polymer of hexamethylenetetramine (HMTA) and polyethylenimine (PEI), and the polymer interrupts the side growth of the nanoseed layer 31 and does not interrupt the axis direction growth of the nanoseed layer 31 when progressing a hydrothermal reaction such that a plurality of nanowires 310 are formed at the predetermined interval on the substrate 100.
The polymer is removed from the nanoshell layer 32 enclosing the nanowires 310 when progressing the hydrothermal reaction such that the side growth and the axis direction growth of the nanoshell layer 32 both progress. Accordingly, the nanobranches 320 are grown on all sides of a plurality of nanowires 310.
Also, the polymer is removed at the side surface of the grown nanobranches 320 such that the side growth and the axis direction growth of the nanoshell layer 33 remaining at the nanobranches 320 both progress. Accordingly, the sub-nanobranches 330 are grown on all sides of a plurality of nanobranches 320.
Therefore, the specific surface area of the nanostructure 300 is widened by the nanowires 310, the nanobranches 320, and the sub-nanobranches 330.
As a variables determining the efficiency of the solar cell, there are an open circuit voltage (Voc), a short circuit current density (Jsc), a fill factor (FF), and efficiency (η).
The open voltage Voc is a potential difference between both terminals of the solar cell when receiving light in a state in which a circuit is opened, that is, an infinite impedance is applied, and the short circuit current density (Jsc) is a current density of a reverse direction (a negative value) in a state when the circuit is shorted, that is, an external resistance does not exist.
Also, the fill factor (FF) as a value of a product of the current density and the voltage value at a maximum power point divided by a product of the open circuit voltage (Voc) and the short circuit current density (Jsc), and is an index representing how the shape of a J-Va curve is close to a quadrangle in a state that light is applied, and the efficiency (η) of the solar cell is a ratio between maximum power produced by the solar cell and the incident light energy.
As shown in
As described above, the solar cell according to an exemplary embodiment of the present invention includes the photoelectrode 1000 made of the nanostructure 300 consisting of the nanowires 310, the nanobranches 320, and the sub-nanobranches 330 to maximally increase the specific surface area such that the dye deposition ratio and the light absorption ratio may be improved, thereby improving the energy conversion efficiency.
While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2011-0063970 | Jun 2011 | KR | national |
