WO2011118890A1

WO2011118890A1 - Tandem solar cell and method of manufacturing the same

Info

Publication number: WO2011118890A1
Application number: PCT/KR2010/006339
Authority: WO
Inventors: Dong-Won Park; Seung-Hyeon Moon; Yonkil Jeong; Hee-Sang Shim; Seung-Hwan Oh; Jae-Kwang Lee
Original assignee: Gwangju Institute of Science and Technology
Current assignee: Gwangju Institute of Science and Technology
Priority date: 2010-03-26
Filing date: 2010-09-16
Publication date: 2011-09-29
Anticipated expiration: 2012-09-26
Also published as: KR101089587B1; KR20110108154A

Abstract

Provided is a tandem solar cell including different kinds of solar cells and a method of manufacturing the same. The tandem solar cell includes an inorganic solar cell constituted by a compound semiconductor including a p-type compound semiconductor layer and a n-type compound semiconductor layer disposed on a lower electrode, an intermediate electrode disposed on the inorganic solar cell, and an organic solar cell disposed on the intermediate electrode and having an upper electrode on a surface thereof opposite to the intermediate electrode.

Description

TANDEM SOLAR CELL AND METHOD OF MANUFACTURING THE SAME

The present invention relates to a tandem solar cell and a method of manufacturing the same, and more particularly, to a tandem solar cell including different kinds of solar cells and a method of manufacturing the same.

Nowadays in the 21^st Century, due to a speedy rising of oil prices, exhaustion of fossil fuels, emission controls of carbon dioxide, etc., consciousness of an energy exhaustion crisis is largely increasing, and thus, necessity for chemical-free and environmentally friendly alternative energy such as solar cells are becoming important issues.

In general, the solar cells absorb unlimited sunlight using semiconductor devices to convert the sunlight into electricity through a photoelectric effect. Since sunlight is free and environmentally friendly, the solar cells have attracted attention as alternative energy sources.

Meanwhile, since conventional solar cells absorb radiation energy of a short wavelength of light, a long wavelength of light cannot be used.

In order to solve this problem, development of solar cells capable of absorbing radiation energy of light having various wavelengths is needed.

In order to solve the foregoing and/or other problems, it is an aspect of the present invention to provide a tandem solar cell including different kinds of solar cells having a good photoelectric effect and capable of manufacturing at a low cost, and a method of manufacturing the same.

The foregoing and/or other aspects of the present invention may be achieved by providing a tandem solar cell including: an inorganic solar cell constituted by a compound semiconductor including a p-type compound semiconductor layer and a n-type compound semiconductor layer disposed on a lower electrode; an intermediate electrode disposed on the inorganic solar cell; and an organic solar cell disposed on the intermediate electrode and having an upper electrode on a surface thereof opposite to the intermediate electrode.

The p-type compound semiconductor layer and the n-type compound semiconductor layer may be any III-V compound semiconductor layer selected from the group consisting of metamorphic InGaP, InGaAs and InGaN.

The intermediate electrode may include a metal nanoparticle, and preferably, may include at least one nanoparticle selected from the group consisting of platinum (Pt), gold (Au), silver (Ag), nickel (Ni), indium (In), and an alloy thereof.

The intermediate electrode may have a grid pattern shape.

The organic solar cell may include a metal oxide layer disposed on a surface of the upper electrode directed to the intermediate electrode and including a metal oxide particle and a photosensitive adsorbent adsorbed to the metal oxide particle; and an electrolyte layer in contact with a surface of the metal oxide layer directed to the inorganic solar cell.

The electrolyte layer may include electrolyte in any one state selected from liquid, solid and quasi-solid including a halogen-based redox couple.

The inorganic solar cell may include the lower electrode; the p-type compound semiconductor layer disposed on the lower electrode; and the n-type compound semiconductor layer disposed on the p-type compound semiconductor layer.

The organic solar cell may include an active layer containing an electron donor and an electron acceptor disposed between the intermediate electrode and the upper electrode.

The active layer may include at least one electron donor selected from the group consisting of poly-3-hexylthiophene (P3HT), poly[2-methyl,5-(3',7'-dimethyloc tyloxy)]-1,4-phenylenevinylene (MDMO-PPV) and poly[2-methoxy,5-(2-ethyl-hexyloxy)1,4 phenylenevinylene] (MEH-PPV); and an electron acceptor formed of a mixture of C₆₀ derivatives.

The inorganic solar cell may include the lower electrode; the n-type compound layer disposed on the lower electrode; and the p-type compound semiconductor layer on the n-type compound semiconductor layer.

The tandem solar cell may further include a hole transport layer disposed between the active layer and the upper electrode.

In addition, a method of manufacturing a tandem solar cell in accordance with the present invention includes: forming a p-type compound semiconductor layer and an n-type compound semiconductor layer on a lower electrode to form an inorganic solar cell; forming an intermediate electrode on the inorganic solar cell; and forming an organic solar cell having an upper electrode on a surface thereof opposite to the intermediate electrode on the intermediate electrode.

Forming the intermediate electrode may include printing a colloid solution including a metal nanoparticle into a grid pattern; and heat-treating the printed colloid solution.

Forming the inorganic solar cell may include forming a p-type compound semiconductor layer and an n-type compound semiconductor layer on a lower electrode through metamorphic crystal growth; removing a substrate from the p-type compound semiconductor layer and the n-type compound semiconductor layer; and adhering the p-type compound semiconductor layer and the n-type compound semiconductor layer, from which the substrate is removed, to a different kind of substrate.

Forming the organic solar cell may include forming a hole transport layer on the upper electrode; and forming an active layer on the hole transport layer.

Forming the organic solar cell may include forming a metal oxide layer on the upper electrode; positioning the metal oxide layer to be spaced apart from the inorganic solar cell; and injecting an electrolyte into the spaced space to form an electrolyte layer.

According to the present invention, it is possible to provide a tandem solar cell including different kinds of solar cells having a good photoelectric effect and capable of manufacturing at a low cost, and a method of manufacturing the same.

Example embodiments of the present invention will become more apparent by describing in detail example embodiments of the present invention with reference to the accompanying drawings, in which:

FIG. 1 is a cross-sectional view for explaining a tandem solar cell in accordance with an example embodiment of the present invention;

FIG. 2 is a cross-sectional view for explaining a tandem solar cell in accordance with another example embodiment of the present invention;

FIGS. 3 to 6 are cross-sectional views for explaining a method of manufacturing a tandem solar cell in accordance with another example embodiment of the present invention;

FIG. 7 is a cross-sectional view for explaining a tandem solar cell in accordance with still another example embodiment of the present invention;

FIGS. 8 to 11 are cross-sectional views for explaining a method of manufacturing a tandem solar cell in accordance with still another example embodiment of the present invention; and

FIG. 12 is a graph for explaining incident photoelectric conversion efficiency of materials used in a tandem solar cell of the present invention.

Example embodiments of the present invention are disclosed herein. However, specific structural and functional details disclosed herein are merely representative for purposes of describing example embodiments of the present invention, however, example embodiments of the present invention may be embodied in many alternate forms and should not be construed as limited to example embodiments of the present invention set forth herein.

Accordingly, while the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit the invention to the particular forms disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like numbers refer to like elements throughout the description of the figures.

It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the present invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (i.e., "between" versus "directly between", "adjacent" versus "directly adjacent", etc.).

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises", "comprising,", "includes" and/or "including", when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

It should also be noted that in some alternative implementations, the functions/acts noted in the blocks may occur out of the order noted in the flowcharts. For example, two blocks shown in succession may in fact be executed substantially concurrently or the blocks may sometimes be executed in the reverse order, depending upon the functionality/acts involved.

FIG. 1 is a cross-sectional view for explaining a tandem solar cell in accordance with an example embodiment of the present invention.

Referring to FIG. 1, a tandem solar cell in accordance with an example embodiment of the present invention includes an inorganic solar cell 130, an organic solar cell 110, and an intermediate electrode 120 between the inorganic solar cell 130 and the organic solar cell 110.

The inorganic solar cell 130 may be a compound semiconductor solar cell, and more particularly, may be a III-V group compound semiconductor solar cell that can use different kinds of substrates.

The inorganic solar cell 130 includes a p-type compound semiconductor layer 132, and an n-type compound semiconductor layer 131 disposed on the p-type compound semiconductor layer 132. Here, the p-type compound semiconductor layer 132 and the n-type compound semiconductor layer 131 are any III-V group compound semiconductor layer selected from the group consisting of metamorphic InGaP, InGaAs and InGaN or a GaAs-based compound semiconductor layer which forms a p-n junction.

While the structure in which the n-type compound semiconductor layer 131 is disposed on the p-type compound semiconductor layer 132 has been described, the present invention is not limited thereto. For example, the p-type compound semiconductor layer 132 may be disposed on the n-type compound semiconductor layer 131.

A lower substrate 134 including a lower electrode 133 is provided under the p-type compound semiconductor layer 132, and the lower electrode 133 is in contact with the p-type compound semiconductor layer 132.

Here, the lower electrode 133 may be formed of a transparent conductive material, and preferably, may be formed of at least one selected from the group consisting of fluorine doped tin oxide (FTO), indium tin oxide (ITO), indium zinc oxide (IZO), ZnO, Al-doped zinc oxide (AZO), SnO₂ and Mo.

In addition, the lower substrate 134 may be formed of a transparent or opaque material. Here, when the lower substrate 134 is formed of a transparent material, the lower substrate 134 may be a transparent glass or transparent polymer film. The transparent polymer film may be any one selected from the group consisting of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polypropylene (PP) and polyimide (PI).

The intermediate electrode 120 prevents generation and diffusion of a depletion layer, which may cause an increase in energy barrier at an interface between the organic solar cell 110 and the inorganic solar cell 130. That is, the intermediate electrode 120 may enable tunneling movement of electrons and holes between the organic solar cell 110 and the inorganic solar cell 130 to increase efficiency of the tandem solar cell.

The intermediate electrode 120 may be a metal nanoparticle, and more particularly, may be any one nanoparticle selected from the group consisting of Pt, Au, Ag, Ni, In and an alloy thereof. This is because generation of the depletion layer can be minimized as a contact area between the intermediate electrode 120 and the n-type compound semiconductor layer 131 becomes smaller in comparison with an area in which the intermediate electrode 120 is formed.

In addition, the intermediate electrode 120 may have a grid pattern shape. The grid pattern-shaped intermediate electrode 120 may be formed by printing a colloid solution including a metal nanoparticle into a grid pattern and then heat-treating the colloid solution. In addition, a grid pattern-shaped intermediate electrode 120 may be formed through a chemical mechanical deposition method using a mask pattern having a region opened in the grid pattern shape.

Here, the organic solar cell 110 may contact the inorganic solar cell 130 at a region in which the intermediate electrode 120 is not formed, generating a depletion layer. Therefore, movement of charges may be restricted at a region in which the organic solar cell 110 is adhered to the inorganic solar cell 130 due to the depletion layer. However, since most of the charges move through the intermediate electrode 120, there is no influence on device characteristics of the tandem solar cell in accordance with an example embodiment of the present invention.

In addition, the intermediate electrode 120 may have a thickness range that allows light transmission.

The organic solar cell 110 may be constituted by a dye-sensitized solar cell or an organic solar cell.

The organic solar cell 110 includes an upper substrate 111, an upper electrode 112 disposed on the upper substrate 111, and a layer for generating electrons and holes using light irradiated from the exterior, with reference to the direction of the inorganic solar cell 130.

As shown in FIG. 1, the layer for generating electrons and holes may include an electron acceptor layer 113 and an electron donor layer 114 disposed on the upper electrode 112, or may be formed into a single layer structure having characteristics of both an electron acceptor and an electron donor.

When the layer for generating electrons and holes includes the electron acceptor layer 113 and the electron donor layer 114, the electron donor layer 114 is directed toward the intermediate electrode 120 to be electrically connected to the inorganic solar cell 130.

The upper substrate 111 may be formed of a transparent glass or transparent polymer film. The transparent polymer film may be any one selected from the group consisting of PET, PEN, PP and PI.

The upper electrode 112 may be formed of a metal material having a lower work function than the lower electrode 133. For example, the upper electrode 112 may be any one selected from the group consisting of Pt, Au, Ag, Ni, In and an alloy thereof.

While the upper electrode 112 formed of a metal material having a lower work function than the lower electrode 133 has been described for the illustrative purpose, the present invention is not limited thereto. For example, when the n-type compound semiconductor layer 131 is disposed on the p-type compound semiconductor layer 132, the lower electrode 133 may be formed of a metal material having a lower work function than the upper electrode 112.

FIG. 2 is a cross-sectional view for explaining a tandem solar cell in accordance with another example embodiment of the present invention, and FIGS. 3 to 6 are cross-sectional views for explaining a method of manufacturing a tandem solar cell in accordance with another example embodiment of the present invention.

Referring to FIGS. 2 and 3 to 6, a tandem solar cell in accordance with another example embodiment of the present invention is similar to that in accordance with an example embodiment of the present invention shown in FIG. 1, except that an organic solar cell 210 is a dye-sensitized solar cell.

Hereinafter, a method of manufacturing a tandem solar cell in accordance with another example embodiment of the present invention will be described in detail.

First, as shown in FIG. 3, an inorganic solar cell 230 is formed. More specifically describing formation of the inorganic solar cell 230, first, a p-type compound semiconductor layer 232 is formed on a substrate through metamorphic crystal growth, and an n-type compound semiconductor layer 231 is formed on the p-type compound semiconductor layer 232 to form a p-n junction structure. Next, the p-n junction structure is separated from the substrate using an epitaxial lift-off (ELO) method. After separating the substrate, a lower electrode 233 formed on the lower substrate 234 is coupled to the p-type compound semiconductor layer 232 to form the inorganic solar cell 230.

After forming the inorganic solar cell 230, an intermediate electrode 220 is formed on the n-type semiconductor layer 231.

While the method of forming the inorganic solar cell 230 and then forming the intermediate electrode 220 has been described, the present invention is not limited thereto. For example, the intermediate electrode 220 may be previously formed on the n-type semiconductor layer 231, the substrate may be separated, and then, the n-type semiconductor layer 231 may be adhered to the lower electrode 233.

After forming the intermediate electrode 220, as shown in FIG. 4, an upper electrode 212 is formed on an upper substrate 211, and then, a metal oxide layer 213 is formed on the upper electrode 212 to form a portion of the organic solar cell 210.

Here, the metal oxide layer 213 includes a base particle 213a, and a photosensitive adsorbent 213b adsorbed and coated to the base particle 213a.

The base particle 213a may be formed of any one metal oxide or a complex oxide selected from the group consisting of Ti, Zr, Sr, Zn, V, W, Sn, Al, Mg and Ga. Preferably, the base particle 213a may be formed of any one selected from the group consisting of titanium oxide (TiO₂), zinc oxide (ZnO), tin oxide (SnO₂), and tungsten oxide (WO₃).

The photosensitive adsorbent 213b may be a dye capable of absorbing visible light, infrared light and ultraviolet light. The dye may be ruthenium (Ru) complexes, and the ruthenium complexes may be N3, N719 and N749. An adsorption method of the dye may be a method used in a conventional dye-sensitized solar cell. Meanwhile, the present invention does not limit the kinds of dyes, and all dyes that can be used in conventional dye-sensitized solar cells may be satisfactorily used.

In addition, the photosensitive adsorbent 213b may be a material that has a charge separation function, except for the dye, and performs a photosensitive reaction. For example, the photosensitive adsorbent 213b may include a xanthine-based pigment (rhodamine B, rose bengal, eosin, etc.), a cyanine-based pigment, a basic organic dye (tyocyn, methylene blue, cabrillo blue, etc.), a porphyrin-based compound (zinc porphyrin, magnesium porphyrin, manganese porphyrin, cobalt porphyrin, iron porphyrin, etc.), another azo pigment, a phthalocyanine compound, CdSe as inorganic dye, etc., which may be used solely or as a mixture of at least two materials.

A material which the photosensitive adsorbent 213b is adsorbed to the base particle 213a formed of the metal oxide or complex oxide is applied to a thickness of 2 ㎛ to 15 ㎛ through any one method selected from screen printing, doctor blade, spin-coating, ink-jet printing, and spray coating. Since the metal oxide layer 213 has a structure in which the photosensitive adsorbent 213b is adsorbed and coated to the base particle 213a formed of a metal oxide, when the thickness is larger than 15 ㎛, a series resistance is increased, and thus, the increase in series resistance may cause a reduction in conversion efficiency. By limiting the thickness as described above, it is possible to prevent a reduction in photoelectric conversion efficiency of the solar cell.

In addition, the material in which the photosensitive adsorbent 213b is adsorbed to the base particle 213a may have a particle size of 10 nm to 25 nm.

After forming a portion of the organic solar cell 210, as shown in FIG. 5, an encapsulant 215 is formed on an edge of the solar cell 230. Here, the encapsulant 215 may be formed of a thermoplastic polymer layer selected from the group consisting of epoxys and silicons, and may have a thickness of 30 ㎛ to 60 ㎛.

After forming the encapsulant 215, the structure shown in FIG. 3, i.e., a portion of the organic solar cell 210, is adhered to the inorganic solar cell 230. Here, the metal oxide layer 213 is inserted into an internal space formed by the encapsulant 215 to be spaced apart a predetermined gap from the inorganic solar cell 230. In addition, upon adhesion, a predetermined amount of heat of 80 ℃ or more is applied to seal a space between the metal oxide layer 213 and the inorganic solar cell 230.

Next, as shown in FIG. 6, an electrolyte is injected through an electrolyte insertion port (not shown) preformed in the space between the metal oxide layer 213 and the inorganic solar cell 230 to form an electrolyte layer 214, thus completing manufacture of a tandem solar cell in accordance with another example embodiment of the present invention.

Here, the electrolyte layer 214 may be formed of an electrolyte that can be permeated into the metal oxide layer 213 to provide an electron. Preferably, the electrolyte layer 214 may be formed of a liquid, solid or quasi-solid electrolyte including a halogen-based redox pair, and more particularly, may be formed of a halogen molecule and halogen salt, or hydroquinone and quinine. For example, the electrolyte 214 may be formed of iodine molecules (I₂) and iodine (I^-) salt, or bromine molecules (Br₂) and bromine (Br^-) salt.

The tandem solar cell in accordance with another example embodiment of the present invention is operated as follows.

First, when light enters the solar cell through the upper substrate 211 from the exterior, at an interface between the metal oxide particles of the metal oxide layer 213 to which dye molecules of the upper cell 210 are adsorbed, electrons and holes are generated at an interface between the n-type compound semiconductor layer 231 and the p-type compound semiconductor layer 232 of the lower cell 230.

The electrons in the upper cell 210 move to the holes of the p-type compound semiconductor layer 232 of the lower cell 230 via an external circuit connected from the upper substrate 211 to the lower substrate 234.

In the metal oxide layer 213 formed of a material which the photosensitive adsorbent 213b is adsorbed to the base particle 213a as a complex oxide, the photosensitive adsorbent 213b oxidized due to electron transition receives electrons provided by an oxidation-reduction reaction (3X^- →X₃ ^-+2e^-) of a halogen ion in the electrolyte layer 214 to be reduced again, and the oxidized halogen ion X₃ ^- is reduced again by electrons arriving at the intermediate electrode 220, thereby completing an operation of the tandem solar cell in accordance with another example embodiment of the present invention.

FIG. 7 is a cross-sectional view for explaining a tandem solar cell in accordance with still another example embodiment of the present invention, and FIGS. 8 to 11 are cross-sectional views for explaining a method of manufacturing a tandem solar cell in accordance with still another example embodiment of the present invention.

Referring to FIGS. 7 and 8 to 11, a tandem solar cell in accordance with still another example embodiment of the present invention is similar to the tandem solar cell in accordance with an example embodiment of the present invention shown in FIG. 1, except that an organic solar cell 310 is an organic semiconductor solar cell, and an inorganic solar cell 330 has a structure in which a p-type compound semiconductor layer 331 is formed on an n-type compound semiconductor layer 332.

Hereinafter, a method of a tandem solar cell in accordance with still another example embodiment of the present invention will be described in detail.

First, as shown in FIG. 8, the inorganic solar cell 330 is formed. A method of forming the inorganic solar cell 330 is as follows. The n-type compound semiconductor layer 332 is formed on a substrate through metamorphic crystal growth, the p-type compound semiconductor layer 331 is formed on the n-type compound semiconductor layer 332, and then the substrate is separated therefrom. Next, a lower electrode 333 formed on a lower substrate 334 is adhered to the n-type compound semiconductor layer 332 to form the inorganic solar cell 330.

After forming the inorganic solar cell 330, an intermediate electrode 320 is formed on the p-type compound semiconductor layer 331.

After forming the intermediate electrode 320, as shown in FIG. 9, the organic solar cell 310 is formed.

In the organic solar cell 310, first, an upper electrode 312 formed of a material having a higher work function than the lower electrode 333 is formed on the upper substrate 311, and a hole transport layer 313 is formed on the upper electrode 312. Here, the upper electrode 312 may be formed of a transparent conductive material, and preferably, may be formed of any one selected from the group consisting of ITO and AZO.

The hole transport layer 313 may be formed of any one selected from the group consisting of polyanilines, polypyrroles, polyphenylene vinylenes, poly(para-phenylenes), polyfluorenes, polyacetylenes, polypyridines, polyalkylthiopenes, polyethylenedioxylthiopenes, and a mixture thereof. The hole transport layer 313 may be formed by various methods because all conventional coating methods of organic materials can be used.

After forming the hole transport layer 313, an active layer 314 is formed on the hole transport layer 313. The active layer 314 may be formed by blending an organic semiconductor material disposed between the upper electrode 312 and the intermediate electrode 320 having a low work function to receive light, generate electrons and holes, and transmit the electrons and the holes. Preferably, the active layer 314 may be formed by blending a material having good electron acceptor characteristics and a material having good electron donor characteristics for absorption of light and formation of excitons. For example, the active layer 314 is formed by blending [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), which is referred to as an electron acceptor having the best performance, as derivatives of C₆₀ deformed to enable a solution process, and poly-3-hexylthiophene (P3HT), poly[2-methyl,5-(3',7'-dimethyloc tyloxy)]-1,4-phenylenevinylene (MDMO-PPV), poly[2-methoxy,5-(2-ethyl-hexyloxy)1,4 phenylenevinylene] (MEH-PPV), etc., which are electron donor subjected to absorption of light and formation of excitons, and applying the blended solution on the hole transport layer 313. The blended solution may be applied using any one selected from spin-coating, ink-jet printing, spray coating, and roll-to-roll printing.

After forming the organic solar cell 310, as shown in FIG. 10, the active layer 314 of the organic solar cell 310 and the n-type compound semiconductor layer 331 of the inorganic solar cell 330 are disposed to oppose each other, and as shown in FIG. 11, the organic solar cell 310 and the inorganic solar cell 330 are electrically connected to each other via the intermediate electrode 320.

While still another embodiment of the present invention has illustrated the method of separately manufacturing the organic solar cell 310 and the inorganic solar cell 330, the present invention is not limited thereto. For example, a method of forming the inorganic solar cell 330, forming the intermediate electrode 320, and sequentially depositing the active layer 314, the hole transport layer 313 and the upper electrode 312 to form the organic solar cell 310 may also be possible.

The tandem solar cell in accordance with still another example embodiment of the present invention is operated as follows.

First, when light is irradiated to the upper substrate 311 from the exterior, the light is irradiated to the active layer 314 of the organic solar cell 310 to transition the electrons in pi bonds to an excited state, and the excited electrons and the holes generated from a place at which the electrons are excited are coupled as pairs to form excitons by Coulomb’s force. The generated excitons are separated such that the electrons move toward the lower electrode 333 having a low work function and the holes move toward the upper electrode 312 having a relatively high work function via the hole transport layer 313.

The electrons generated from the active layer 314 of the organic solar cell 310 and moving toward the lower electrode 333 move to the p-type compound semiconductor layer 331 via the intermediate electrode 320.

The electrons generated from the n-type semiconductor layer of the inorganic solar cell 330 move toward the active layer 314 in an electron-deficient state through an external circuit (not shown) connecting the upper electrode 312 to the lower electrode 333, thereby completing operation of the tandem solar cell in accordance with still another example embodiment of the present invention.

Referring to FIG. 12, it will be appreciated that when a GaAs-based compound semiconductor solar cell is applied to the inorganic solar cell and an organic solar cell P3HT-PCBM or a dye-sensitized solar cell P5, N719 and N749 is applied to the organic solar cell, various wavelength ranges of light can be absorbed to increase energy efficiency of the solar cell.

That is, the inorganic solar cell, to which a compound semiconductor solar cell is applied, absorbs a long wavelength of light to perform photoelectric conversion, and the organic solar cell, to which an organic solar cell or a dye-sensitized solar cell is applied, absorbs a short wavelength of light to perform photoelectric conversion, enabling manufacture of the solar cell having high energy efficiency.

The foregoing description concerns an example embodiment of the invention, is intended to be illustrative, and should not be construed as limiting the invention. The present teachings can be readily applied to other types of devices and apparatuses. Many alternatives, modifications, and variations within the scope and spirit of the present invention will be apparent to those skilled in the art.

Claims

A tandem solar cell comprising:

an inorganic solar cell constituted by a compound semiconductor including a p-type compound semiconductor layer and a n-type compound semiconductor layer disposed on a lower electrode;

an intermediate electrode disposed on the inorganic solar cell; and

an organic solar cell disposed on the intermediate electrode and having an upper electrode on a surface thereof opposite to the intermediate electrode.
The tandem solar cell according to claim 1, wherein the p-type compound semiconductor layer and the n-type compound semiconductor layer are any III-V group compound semiconductor layer selected from the group consisting of metamorphic InGaP, InGaAs and InGaN.
The tandem solar cell according to claim 1, wherein the intermediate electrode comprises a metal nanoparticle.
The tandem solar cell according to claim 3, wherein the intermediate electrode has a grid pattern shape.
The tandem solar cell according to claim 4, wherein the intermediate electrode comprises at least one nanoparticle selected from the group consisting of platinum (Pt), gold (Au), silver (Ag), nickel (Ni), indium (In), and an alloy thereof.
The tandem solar cell according to claim 1, wherein the organic solar cell comprises:

a metal oxide layer disposed on a surface of the upper electrode directed to the intermediate electrode and including a metal oxide particle and a photosensitive adsorbent adsorbed to the metal oxide particle; and

an electrolyte layer in contact with a surface of the metal oxide layer directed to the inorganic solar cell.
The tandem solar cell according to claim 6, wherein the electrolyte layer comprises an electrolyte in any one state selected from liquid, solid and quasi-solid including a halogen-based redox pair.
The tandem solar cell according to claim 6, wherein the inorganic solar cell comprises:

the lower electrode;

the p-type compound semiconductor layer disposed on the lower electrode; and

the n-type compound semiconductor layer disposed on the p-type compound semiconductor layer.
The tandem solar cell according to claim 1, wherein the organic solar cell comprises an active layer containing an electron donor and an electron acceptor disposed between the intermediate electrode and the upper electrode.
The tandem solar cell according to claim 9, wherein the active layer comprises;

at least one electron donor selected from the group consisting of poly-3-hexylthiophene (P3HT), poly[2-methyl,5-(3',7'-dimethyloc tyloxy)]-1,4-phenylenevinylene (MDMO-PPV) and poly[2-methoxy,5-(2-ethyl-hexyloxy)1,4 phenylenevinylene] (MEH-PPV); and

an electron acceptor formed of a mixture of C₆₀ derivatives.
The tandem solar cell according to claim 9, wherein the inorganic solar cell comprises:

the lower electrode;

the n-type compound layer disposed on the lower electrode; and

the p-type compound semiconductor layer on the n-type compound semiconductor layer.
The tandem solar cell according to claim 9, further comprising a hole transport layer disposed between the active layer and the upper electrode.
A method of manufacturing a tandem solar cell, comprising:

forming a p-type compound semiconductor layer and an n-type compound semiconductor layer on a lower electrode to form an inorganic solar cell;

forming an intermediate electrode on the inorganic solar cell; and

forming an organic solar cell having an upper electrode on a surface thereof opposite to the intermediate electrode on the intermediate electrode.
The method according to claim 13, wherein forming the intermediate electrode comprises:

printing a colloid solution including a metal nanoparticle into a grid pattern; and

heat-treating the printed colloid solution.
The method according to claim 13, wherein forming the inorganic solar cell comprises:

forming a p-type compound semiconductor layer and an n-type compound semiconductor layer on a lower electrode through metamorphic crystal growth;

removing a substrate from the p-type compound semiconductor layer and the n-type compound semiconductor layer; and

adhering the p-type compound semiconductor layer and the n-type compound semiconductor layer, from which the substrate is removed, to a different kind of substrate.
The method according to claim 13, wherein forming the organic solar cell comprises:

forming a hole transport layer on the upper electrode; and

forming an active layer on the hole transport layer.
The method according to claim 13, wherein forming the organic solar cell comprises:

forming a metal oxide layer on the upper electrode;

positioning the metal oxide layer to be spaced apart from the inorganic solar cell; and

injecting an electrolyte into the spaced space to form an electrolyte layer.