KR102006074B1 - Solar cell including nanowire array and manufacturing method thereof - Google Patents

Abstract

The present invention discloses a solar cell comprising a nanowire array and a method of manufacturing the same. A solar cell including a nanowire array includes: a semiconductor layer of a first polarity formed on a lower electrode; A semiconductor layer of a second polarity formed on the semiconductor layer of the first polarity and having a polarity different from the polarity of the first polarity; And an upper electrode formed on the second polarity semiconductor layer, wherein the lower electrode and the upper electrode are a nanowire array including at least one nanowire, and the nanowire array comprises: And has the same polarity as that of the first polarity semiconductor layer or the second polarity semiconductor layer which are directly in contact with each other.

Description

TECHNICAL FIELD [0001] The present invention relates to a solar cell including a nanowire array and a method of manufacturing the solar cell.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell including a nanowire array and a manufacturing method thereof, and more particularly, to a solar cell including a highly efficient nanowire array capable of reducing manufacturing cost and a manufacturing method thereof .

Today, due to high oil prices and environmental pollution, development of clean alternative energy is urgent. Among various alternative energies, the use of solar energy is recognized as the most economical way, and there is a growing interest in solar cells that convert optical energy directly into electrical energy.

The structure of a silicon solar cell is composed of an antireflection film (AR coating) for allowing solar light to be absorbed into the silicon substrate and an antireflection film (AR coating) inside the solar cell , And a P-layer). In a silicon solar cell, a p-type junction is formed by forming an n-type semiconductor by diffusing a Group 5 element on its surface based on p-type silicon. When the solar light is absorbed on the substrate where the pn junction is formed, an electronholepair (EHP) is formed and freely moves. When the electron enters the electric field generated by the pn junction, the hole (+) is p- the electrons move to the n-type and a potential is generated, and the generated electron mobility causes a current to flow to the external conductor through the electrodes at both ends.

Solar cells are fabricated on the basis of polycrystalline or monocrystalline silicon wafers, and thin-film structures are being studied for high efficiency solar cells. However, bulk solar cells with a thickness of 150 mm or more have a disadvantage of high manufacturing costs. However, Since the thickness is less than 2 탆, the material cost can be lowered compared with the bulk solar cell.

 Thin film solar cells have a PN junction structure, but have a disadvantage in that they are less efficient than bulk solar cells. However, a method for complementing them is a technique of making a pattern on the top (light incoming side) by etching or a multi- Solar cell technology is being studied.

Specifically, as a method for improving the efficiency of a solar cell, a method of suppressing the reflectance of sunlight is being developed, and a dry concave convex texture is mainly formed by the vapor phase method to reduce the reflectance to about 10 to 20% A method for improving the efficiency is being studied.

Conventionally, there is a method of forming an antireflection film on a surface of a solar cell or forming a nanostructure on the surface of a solar cell by improving the photovoltaic efficiency characteristic by maximizing reduction of the solar light reflectance for increasing the efficiency of the solar cell.

As a method of forming the antireflection film, silicon nitride (SINx) is deposited on a light receiving portion of a solar cell by using a chemical vapor deposition (CVD) method, and silicon nitride is patterned by a dry etching method using plasma or a wet etching method A method of forming a protective film is a typical example. The wet etching method is mainly used for the low production cost of the solar cell among the dry etching method and the wet etching method. However, the dry etching method and the wet etching method are difficult to form a pattern, .

As a method of forming the nanostructure, there is a Vapor-Liquid-Solid (VLS) method, which is mainly manufactured by growing nanowires, and a method of forming a nanostructure by a wet-dry etching process using a porous mask .

When the nanowire is manufactured by the conventional VLS method, the array of nanowires becomes irregular, and even if the optimized solar cell passivation (doping and TCO process) is applied, the nanowire arrays become denser due to the nano- An etching method has been proposed as a method for arraying nanowires with limitations. Here, the method of forming a nanostructure using a porous mask is advantageous in that it can form a uniform arrangement and a vertical nanostructure, but it is limited because it is difficult to form a polycrystalline silicon thin film on a low-cost substrate such as a glass substrate.

In addition, it has been confirmed that the antireflection layer of the silicon absorbing layer manufactured by the conventional method is suitable for small-scale production as a relatively expensive production technology and has a limit to the lowering of the reflectance which directly affects the solar light efficiency.

Korean Patent No. 10-1100414, "Solar cell and its manufacturing method" Korean Patent No. 10-1401887, "Solar cell and method for manufacturing the same" Korean Patent No. 10-1465397, "Solar cell"

An object of embodiments of the present invention is to improve the efficiency while reducing the manufacturing cost of a solar cell by growing a nanowire array including at least one nanowire on a growth substrate and then transferring it onto a bulk layer .

An object of embodiments of the present invention is to improve the light absorption rate of a solar cell by using a nanowire array including at least one nanowire as an anti-reflection layer and an electrode of a solar cell.

A solar cell including a nanowire array according to an embodiment of the present invention includes: a first polarity semiconductor layer formed on a lower electrode; A semiconductor layer of a second polarity formed on the semiconductor layer of the first polarity and having a polarity different from the polarity of the first polarity; And an upper electrode formed on the second polarity semiconductor layer, wherein the lower electrode or the upper electrode is a nanowire array including at least one nanowire, And has the same polarity as the first polarity semiconductor layer or the second polarity semiconductor layer directly contacting.

The nanowire array can refract the incident light.

The nanowire arrays may be regularly arranged to have a constant period, or randomly arranged.

The space filling ratio of the at least one nanowire may be 10% or more.

The diameter of the at least one nanowire may be between 10 nm and 100 nm.

The nanowire array may be formed in multiple layers.

The upper electrode may further include a sub electrode partially covering the upper electrode.

The lower electrode may further include a sub electrode.

The at least one nanowire may include at least one of a group IV semiconductor semiconductor, a group III-V group, and a group II-VI semiconductor.

A solar cell including a nanowire array according to another embodiment of the present invention includes: a first polarity semiconductor layer formed on a lower electrode; And an upper electrode formed on the semiconductor layer of the first polarity, wherein the lower electrode or the upper electrode is a nanowire array including at least one nanowire, the nanowire array includes a first polarity semiconductor layer, And may have a second polarity having a different polarity.

The nanowire array can refract the incident light.

A method of fabricating a solar cell including a nanowire array according to an embodiment of the present invention includes forming a first polarity semiconductor layer on a lower electrode; Forming a second polarity semiconductor layer having a polarity different from the first polarity on the first polarity semiconductor layer; And transitioning an upper electrode on the second polarity semiconductor layer, wherein the upper electrode is a nanowire array comprising at least one nanowire, the nanowire array having a second polarity And has the same polarity as the semiconductor layer.

The step of transitioning the upper electrode on the second polarity semiconductor layer includes growing a second polarity nanowire on the growth substrate; Obtaining the grown nanowires of the second polarity; And transferring the obtained second polarity nanowires onto a second polarity semiconductor layer to form a second polarity nanowire array.

The step of transferring the separated second polarity nanowires on the second polarity semiconductor layer to form the nanowire array of the second polarity may be repeated at least once.

The second polarity of the nanowire may be formed by a chemical vapor deposition (CVD) method, a vapor-liquid-solid method, a thermal chemical vapor deposition (T-CVD) A rapid thermal chemical vapor deposition (RTCVD), a plasma enhanced chemical vapor deposition (PECVD), an inductively coupled enhanced chemical vapor deposition (ICPCVD), an organic metal chemical vapor deposition (MOCVD), low pressure chemical vapor deposition (LPCVD), catalyst-free MOCVD, atmospheric pressure chemical vapor deposition (APCVD) ), Sputtering, thermal or electron beam evaporation, and pulse laser deposition. Can to be stored.

The second polarity nanowire may be at least one of spin coating, physical vapor transport, drop casting, solvent annealing, shear force transfer, and contact printing. Can be transferred in one way.

According to the embodiments of the present invention, the nanowire array including at least one nanowire on the growth substrate is grown, and then transferred onto the bulk layer, thereby reducing the manufacturing cost of the solar cell and improving the efficiency .

According to embodiments of the present invention, the nanowire array including at least one nanowire is used as an anti-reflection layer and an electrode of a solar cell, thereby improving the light absorption rate of the solar cell.

1A and 1B are cross-sectional views illustrating a solar cell including a nanowire array according to an embodiment of the present invention including a nanowire array on top.
FIGS. 2A and 2B are cross-sectional views illustrating a solar cell including a nanowire array according to an embodiment of the present invention including a nanowire array at the bottom.
3A and 3B are plan views showing the arrangement structure of the nanowire array.
4 is a cross-sectional view of a nanowire having a circular cross-sectional structure.
5A and 5B are cross-sectional views illustrating a solar cell including a nanowire array according to an embodiment of the present invention including a nanowire array on top.
6A is an optical microscope image showing a nanowire array of a solar cell including a nanowire array according to an embodiment of the present invention in which the nanowires are randomly arranged.
FIG. 6B is an electron microscope image showing a nanowire array of a solar cell including a nanowire array according to an embodiment of the present invention randomly arranged in a specific region. FIG.
6C is an electron microscope image showing a nanowire array of a solar cell including a nanowire array according to an embodiment of the present invention arranged in a multilayer structure.
FIG. 7A is a three-dimensional diagram showing the axis of the nanowire, and FIGS. 7B and 7C are graphs showing the wavelength-reflectance characteristics of a solar cell including a nanowire array according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings and accompanying drawings, but the present invention is not limited to or limited by the embodiments.

The terminology used herein is for the purpose of illustrating embodiments and is not intended to be limiting of the invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. It is noted that the terms "comprises" and / or "comprising" used in the specification are intended to be inclusive in a manner similar to the components, steps, operations, and / Or additions.

As used herein, the terms "embodiment," "example," "side," "example," and the like should be construed as advantageous or advantageous over any other aspect or design It does not.

Also, the term 'or' implies an inclusive or 'inclusive' rather than an exclusive or 'exclusive'. That is, unless expressly stated otherwise or clear from the context, the expression 'x uses a or b' means any of the natural inclusive permutations.

Also, the phrase "a" or "an ", as used in the specification and claims, unless the context clearly dictates otherwise, or to the singular form, .

The terms used in the following description are chosen to be generic and universal in the art to which they are related, but other terms may exist depending on the development and / or change in technology, customs, preferences of the technician, and the like. Accordingly, the terminology used in the following description should not be construed as limiting the technical thought, but should be understood in the exemplary language used to describe the embodiments.

Also, in certain cases, there may be a term chosen arbitrarily by the applicant, in which case the detailed description of the meaning will be given in the corresponding description section. Therefore, the term used in the following description should be understood based on the meaning of the term, not the name of a simple term, and the contents throughout the specification.

On the other hand, the terms first, second, etc. may be used to describe various elements, but the elements are not limited by terms. Terms are used only for the purpose of distinguishing one component from another.

It will also be understood that when an element such as a film, layer, region, configuration request, etc. is referred to as being "on" or "on" another element, And the like are included.

Unless defined otherwise, all terms (including technical and scientific terms) used herein may be used in a sense commonly understood by one of ordinary skill in the art to which this invention belongs. Also, commonly used predefined terms are not ideally or excessively interpreted unless explicitly defined otherwise.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. The terminology used herein is a term used for appropriately expressing an embodiment of the present invention, which may vary depending on the user, the intent of the operator, or the practice of the field to which the present invention belongs. Therefore, the definitions of these terms should be based on the contents throughout this specification.

Hereinafter, a solar cell including a nanowire array according to an embodiment of the present invention will be described with reference to FIGS. 1A and 2B.

Solar cells generate electrical energy using the photoelectric effect of PN junctions that convert photons of sunlight into electricity. In a solar cell, a lower electrode and an upper electrode are formed on upper and lower surfaces of a semiconductor layer in which a PN junction is formed. Therefore, the solar cell induces the photoelectric effect of the PN junction by the solar light incident on the semiconductor, and the electrons generated therefrom provide a current flowing through the electrode to the outside.

A solar cell including a nanowire array according to an embodiment of the present invention includes a first polarity semiconductor layer 121 and a second polarity semiconductor layer 122 formed on a lower electrode 110, And an upper electrode 140 formed on the semiconductor layers 131 and 132 of the second polarity and the semiconductor layers 131 and 132 of the second polarity,

The lower electrode 110 or the upper electrode 140 is a nanowire array including at least one nanowire 141 and 142 and the nanowire array includes a first polarity semiconductor layer 121, and 122 or the semiconductor layers 131 and 132 of the second polarity.

Since a solar cell including a nanowire array according to an embodiment of the present invention exhibits an optical effect that reduces the reflection of the surface and an electrical effect that smoothes the flow of electric current moving along the surface, By having the same polarity as the first polarity semiconductor layers 121 and 122 or the second polarity semiconductor layers 131 and 132 directly contacted by the nanowire array, the surface resistance can be reduced and the current diffusion can be improved.

Figures 1a and 2b show the same components, except that the nanowire array is used as an upper electrode (see Figure la and Figure 1b) or as a lower electrode (see 2a and Figure 2b) 1a.

In addition, a solar cell including a nanowire array according to an embodiment of the present invention may be formed of a nanowire array in all of the upper and lower electrodes 110 and 140.

1A and 1B are cross-sectional views illustrating a solar cell including a nanowire array according to an embodiment of the present invention including a nanowire array as an upper electrode.

1A is a cross-sectional view of a solar cell including a nanowire array according to an embodiment of the present invention, wherein the first polarity is p-type and includes a nanowire array as an upper electrode.

A solar cell including a nanowire array according to an embodiment of the present invention includes a lower electrode 110.

The lower electrode 110 may be formed of a transparent material and may be formed of a transparent conductive oxide such as a metal, indium tin oxide (ITO), indium zinc oxide (IZO), aluminum zinc oxide (AZO), or indium zinc tin oxide (Al), silver (Ag), gold (Au), nickel (Ni), titanium (Ti), and chromium (Cr). ≪ / RTI >

A solar cell including a nanowire array according to an embodiment of the present invention includes a first polarity semiconductor layer 121 formed on a lower electrode 110.

The first polarity may be p-type or n-type, and the first polarity is p-type in Fig.

Accordingly, the first polarity semiconductor layer 121 of the solar cell including the nanowire array according to an embodiment of the present invention shown in FIG. 1A may be a p-type semiconductor layer.

The semiconductor layer 121 of the first polarity may be formed of a semiconductor compound including a group IV semiconductor such as Si and Ge, a group III-V semiconductor such as InP or GaAs, and at least one of CdS and II-VI group, A dopant of the first polarity may be doped.

When the first polarity is p-type, the dopant of the first polarity is a p-type dopant and may include at least one of Mg, Zn, Ca, Sr, and Ba.

The semiconductor layer 121 of the first polarity may be formed by a method of chemical vapor deposition (CVD), molecular beam epitaxy (MBE), sputtering, and / or vapor phase epitaxy (HVPE).

For example, the semiconductor layer 121 of the first polarity may be formed in the chamber such that the chamber contains a p-type impurity such as trimethyl gallium gas (TMGa), ammonia gas (NH ₃ ), nitrogen gas (N ₂ ), and magnesium Tin cyclopentadienyl magnesium (EtCp2Mg) {Mg (C2H5C5H4) 2} may be implanted to form a p-type GaN layer, but the present invention is not limited thereto.

A solar cell including a nanowire array according to an embodiment of the present invention includes a semiconductor layer 131 of a second polarity formed on a semiconductor layer 121 of a first polarity.

The second polarity may be p-type or n-type, and the second polarity is n-type in Fig.

Accordingly, the second polarity semiconductor layer 121 of the solar cell including the nanowire array according to an embodiment of the present invention shown in FIG. 1A may be an n-type semiconductor layer.

The semiconductor layer 131 of the second polarity may be formed of a semiconductor compound including a group IV semiconductor such as Si and Ge, a group III-V semiconductor such as InP or GaAs, and at least one of CdS and II-VI group, A dopant of the second polarity may be doped.

When the second polarity is n-type, the dopant of the second polarity is an n-type dopant and may include at least one of Si, Ge, Sn, Se and Te, but is not limited thereto.

The semiconductor layer 131 of the second polarity may be formed by a method of chemical vapor deposition (CVD), molecular beam epitaxy (MBE), sputtering, and / or vapor phase epitaxy (HVPE).

For example, the semiconductor layer 131 of the second polarity may be formed of a silane containing an n-type impurity such as trimethyl gallium gas (TMGa), ammonia gas (NH ₃ ), nitrogen gas (N ₂ ) Gas (SiH ₄ ) may be implanted to form the n-type GaN layer, but the present invention is not limited thereto.

A solar cell including a nanowire array according to an embodiment of the present invention includes an upper electrode 140 formed on a semiconductor layer 131 of a second polarity.

The upper electrode 140 is a nanowire array including at least one nanowire 141 and the nanowire array has the same polarity as the second polarity semiconductor layer 131 to which the nanowire array directly contacts.

Accordingly, the nanowire array of a solar cell including the nanowire array according to an embodiment of the present invention shown in FIG. 1A may include n-type nanowires.

The nanowire 141 may include at least one of a circular, triangular, square, pentagonal, and hexagonal cross-sectional structure.

Preferably, the nanowire 141 has a triangular cross-sectional structure, so that the refractive index gradually decreases toward the upper part and the graded index effect that minimizes the reflectance can be improved.

The nanowire 141 may be formed of a semiconductor compound including a Group IV semiconductor such as Si and Ge, a III-V semiconductor such as InP or GaAs, and at least one of CdS and II-VI, The dopant can be doped.

Since a solar cell including a nanowire array according to an embodiment of the present invention exhibits an optical effect that reduces the reflection of the surface and an electrical effect that smoothes the flow of electric current moving along the surface, By having the same polarity as the semiconductor layer 131 of the second polarity to which the nanowire array is directly abutted, the surface resistance can be reduced and the current diffusion can be improved.

In addition, the solar cell including the nanowire array according to an embodiment of the present invention uses the nanowire array as the upper electrode 140, thereby increasing the amount of sunlight that can be absorbed in the solar cell due to reduced surface reflection The surface resistance can be reduced, and the current diffusion can be improved.

In addition, the nanowire arrays may be arranged in a horizontally laid-out configuration when the nanowires are arranged in the semiconductor layer 131 of the second polarity. That is, the axis of the nanowire lies in the plane direction of the semiconductor layer (see FIGS. 3A and 3B, it can be seen that the nanowires are formed horizontally).

The nanowire array can be used as an anti-reflection layer that refracts incident light. Thus, the nanowire array can prevent the reflection of incident light, thereby improving the light absorption efficiency of the solar cell.

In addition, since the solar cell including the nanowire array according to the embodiment of the present invention can obtain the surface texturing effect due to the nanowire array formed on the pn junction semiconductor layers 121 and 131, .

Accordingly, the nanowire array of the solar cell including the nanowire array according to an embodiment of the present invention shown in FIG. 1A may be formed by being transferred on the semiconductor layer 131 of the second polarity.

The technique of transferring the nanowire array onto the semiconductor layer 131 of the second polarity includes growing the nanowires on the growth substrate, separating the grown nanowires and transferring them on the semiconductor layer 131 of the second polarity And the forming method will be described in detail in Figs. 5A and 5B.

The nanowire array can be fabricated by at least one of spin coating, physical vapor transport, drop casting, solvent annealing, shear force transfer, and contact printing Can be transferred.

Accordingly, a solar cell including a nanowire array according to an embodiment of the present invention shown in FIG. 1A is formed by transferring a nanowire array on a bulk-type second polarity semiconductor layer 131 to form a nanowire array It is possible to remove the etching process and improve the light efficiency remarkably.

The nanowire arrays may be regularly arranged or randomly arranged such that the nanowires have a constant period.

The arrangement of the nanowire arrays will be described with reference to FIGS. 3A and 3B.

3A and 3B are plan views showing the arrangement structure of the nanowire array.

As shown in FIG. 3A, the nanowire array of the solar cell including the nanowire array according to the exemplary embodiment of the present invention may be regularly arranged such that at least one nanowire 141 has a constant period, One or more nanowires 141 may be randomly arranged.

As shown in FIG. 3A, when the nanowire array of the solar cell including the nanowire array according to an embodiment of the present invention is regularly arranged so that at least one nanowire 141 has a constant period, There is an effect that the reflectance is further reduced at a specific wavelength.

When at least one or more nanowires 141 are randomly arranged as shown in FIG. 3B, the nanowire array 140 of the solar cell including the nanowire array according to an embodiment of the present invention may have a space filling degree of the nanowire array The surface reflectance is reduced as the refractive index increases to a specific value (preferably about 50%).

In addition, if the nanowire arrays of the solar cells including the nanowire arrays according to an embodiment of the present invention are regularly arranged to have a constant period and the nanowires fill the space without voids, at least one of the nanowires 141 ) May be 10 nm to 300 nm.

The diameter d of the at least one nanowire 141 may be 10 nm to 300 nm and if the diameter d of the at least one nanowire 141 is less than 10 nm, There is a problem in that the surface reflection reduction effect by the nanowire array is not generated, and when it exceeds 300 nm, there arises a back scattering effect by the nanowire array and the surface reflectance is rather increased.

More specifically, if the diameter of the nanowire 141 is larger than the wavelength of light, the reflection characteristic of the light becomes stronger. If the diameter of the nanowire 141 is smaller than the wavelength of the light, the reflection characteristic of the light is reduced.

For example, when the refractive index of the nanowire 141 is n and the wavelength range that the solar cell can absorb is 300 nm to 1100 nm (based on Si material), the maximum wavelength that the solar cell can absorb The diameter of the nanowire 141 should be 1100 / n or less based on 1100 nm. Although the refractive index of the Si material changes depending on the wavelength of light, the nanowire 141 preferably has a maximum diameter of 300 nm because the refractive index of the Si material can be about 4 on average.

When fabricating the nanowire 141, it is difficult to reliably manufacture the nanowire 141 at a thickness of 10 nm or less. Therefore, the minimum diameter of the nanowire 141 may be 10 nm, The size of the nanowire 141 can not be recognized as a structure. Therefore, the maximum diameter of the nanowire 141 is preferably 10 nm.

Preferably, the diameter d of the at least one nanowire 141 may be between 30 nm and 200 nm. When the diameter d of at least one nanowire 141 is out of the range of 30 nm to 200 nm, the effect of reducing the reflection of the surface by the nanowire 141 begins to gradually decrease.

In addition, the space filling ratio of the at least one nanowire 141 may be 10% or more. Since the space filling ratio of the nanowire 141 is 10% or more, the reflectance at the surface can be significantly reduced. In addition, the maximum value of the space filling ratio of the nanowires 141 means a case having a close packed structure.

The space filling ratio of the nanowire 141 will be described with reference to FIG.

Referring again to FIG. 1A, a nanowire array of a solar cell including a nanowire array according to an embodiment of the present invention may be formed in multiple layers.

Accordingly, when a nanowire array of a solar cell including a nanowire array according to an embodiment of the present invention is formed in multiple layers and the nanowire spatial density, size, or material of each layer is adjusted, the refractive index gradually increases toward the top And the graded index effect in which the reflectance is minimized is improved, so that the surface reflection can be reduced to nearly 0 in a wide wavelength range.

For example, a first layer of nanowire arrays (the first formed nanowire array on a semiconductor layer), a second layer of nanowire arrays and a third layer of nanowire arrays (a nanowire array furthest from the semiconductor layer ), The spatial density of the nanowires of each layer is reduced so that from the nanowire array of the first layer to the nanowire array of the third layer (the spatial density of the nanowires: The first layer> the second layer> the third layer), the refractive index gradually decreases from the nanowire array of the multi-layered structure to the upper portion, and a graded index effect is obtained in which the reflectance is minimized. The reflection can be reduced close to zero.

According to an embodiment, a solar cell including a nanowire array according to an embodiment of the present invention includes a top electrode 140 of a nanowire array including at least one nanowire 141, The sub electrode 150 may further include a sub electrode 150.

The sub electrode 150 may include a transparent electrode material or a metal material. When the sub electrode 150 is formed on the upper electrode 140, the sub electrode 150 may serve as a sub- The electrode 150 may be formed to partially cover the upper electrode 140 or the upper electrode 140 may be formed of a nanowire array including at least one nanowire 141, The sub electrode 150 of the metal material is selectively (partially) formed so as to correspond to the area where the nanowire 141 is removed after the nanowire 141 is patterned so that the nanowire 141 is removed can do.

More specifically, if the sub-electrode 150 of the metal material covers all of the upper electrode 140, light is reflected on the entire surface, and the light absorption of the pn junction semiconductor layers 121 and 131 is reduced And the sub electrode 150 covers only a part of the area of the upper electrode 140, it is possible to improve the current diffusion without interfering with the light absorption.

In addition, according to the embodiment, a transparent electrode may be further included between the upper electrode 140 and the sub electrode 150, and the transparent electrode may be formed to cover the entire upper electrode 140.

1B is a cross-sectional view of a solar cell including a nanowire array according to an embodiment of the present invention, wherein the first polarity is n-type and includes a nanowire array as an upper electrode.

2B, the first polarity is the n-type, and the first polarity is the p-type except that the first polarity is the p-type. Therefore, the description of the same components will be omitted.

A solar cell including a nanowire array according to an embodiment of the present invention includes a first polarity semiconductor layer 122 formed on a lower electrode 110.

The first polarity may be p-type or n-type, and in Fig. 1b, the first polarity is n-type.

Accordingly, the first polarity semiconductor layer 122 of the solar cell including the nanowire array according to an embodiment of the present invention shown in FIG. 1B may be an n-type semiconductor layer.

The semiconductor layer 122 of the first polarity may be formed of a semiconductor compound including a group IV semiconductor such as Si and Ge, a group III-V semiconductor such as InP or GaAs, and at least one of CdS and II-VI group, A dopant of the first polarity may be doped.

When the first polarity is n-type, the dopant of the first polarity is an n-type dopant and may include at least one of Si, Ge, Sn, Se and Te, but is not limited thereto.

For example, the semiconductor layer 122 of a first polarity is a silane containing n-type impurities such as trimethyl gallium gas (TMGa), ammonia gas (NH _3), nitrogen gas (N ₂₎ and silicon (Si) into the chamber Gas (SiH ₄ ) may be implanted to form the n-type GaN layer, but the present invention is not limited thereto.

A solar cell comprising a nanowire array according to an embodiment of the present invention includes a second polarity semiconductor layer 132 formed on a first polarity semiconductor layer 122.

The second polarity may be p-type or p-type, and in Fig. 1b, the second polarity is p-type.

Accordingly, the second polarity semiconductor layer 132 of the solar cell including the nanowire array according to an embodiment of the present invention shown in FIG. 1B may be a p-type semiconductor layer.

The semiconductor layer 132 of the second polarity may be formed of a semiconductor compound including a group IV semiconductor such as Si and Ge, a group III-V semiconductor such as InP or GaAs, and at least one of CdS and II-VI group, A dopant of the second polarity may be doped.

When the second polarity is p-type, the dopant of the second polarity is a p-type dopant and may include at least one of Mg, Zn, Ca, Sr, and Ba.

For example, the semiconductor layer 132 of the second polarity may be formed in the chamber such that the chamber contains a p-type impurity such as trimethyl gallium gas (TMGa), ammonia gas (NH ₃ ), nitrogen gas (N ₂ ), and magnesium Tin cyclopentadienyl magnesium (EtCp2Mg) {Mg (C2H5C5H4) 2} may be implanted to form a p-type GaN layer, but the present invention is not limited thereto.

A solar cell comprising a nanowire array according to an embodiment of the present invention includes an upper electrode 140 formed on a semiconductor layer 132 of a second polarity.

The upper electrode 140 is a nanowire array that includes at least one nanowire 142 and the nanowire array has the same polarity as the second polarity semiconductor layer 132 that directly contacts.

Accordingly, the nanowire array of a solar cell including the nanowire array according to an embodiment of the present invention shown in FIG. 1B may include a p-type nanowire.

The nanowire may be formed of a semiconductor compound including a Group IV semiconductor such as Si and Ge, a III-V semiconductor such as InP or GaAs, and at least one of CdS and II-VI groups, and the dopant of the second polarity may be doped .

Since a solar cell including a nanowire array according to an embodiment of the present invention exhibits an optical effect that reduces the reflection of the surface and an electrical effect that smoothes the flow of electric current moving along the surface, By having the same polarity as the second polarity semiconductor layer 132 to which the nanowire array directly contacts, it is possible to reduce surface resistance and improve current diffusion.

The nanowire array can be used as an anti-reflection layer that refracts incident light. Thus, the nanowire array can prevent the reflection of incident light, thereby improving the light absorption efficiency of the solar cell.

In addition, the solar cell including the nanowire array according to an embodiment of the present invention can obtain the surface texturing effect due to the nanowire array formed on the pn junction semiconductor layers 122 and 132, thereby improving the light extraction efficiency .

Accordingly, the nanowire array of the solar cell including the nanowire array according to an embodiment of the present invention shown in FIG. 1B may be formed on the semiconductor layer 132 of the second polarity.

According to an embodiment, a solar cell including a nanowire array according to an embodiment of the present invention includes a top electrode 140 of a nanowire array including at least one nanowire 142, The sub electrode 150 may further include a sub electrode 150.

The sub-electrode 150 may include a transparent electrode material or a metal material. When the sub-electrode 150 is formed on the upper electrode 140, the sub- May be formed to partially cover the upper electrode 140 or to form an upper electrode 140 of a nanowire array including at least one nanowire 142, After the nanowire 142 is patterned to be removed (not arranged), the sub electrode 150 of a metal material may be selectively formed to correspond to the area where the nanowire 142 is removed.

More specifically, when the sub electrode 150 of a metal material covers all of the upper electrode 140, light is totally reflected on the surface, so that the light absorption of the pn junction semiconductor layers 122 and 132 is reduced And the sub electrode 150 covers only a part of the area of the upper electrode 140, it is possible to improve the current diffusion without interfering with the light absorption.

In addition, according to the embodiment, a transparent electrode may be further included between the upper electrode 140 and the sub electrode 150, and the transparent electrode may be formed to cover the entire upper electrode 140.

2A and 2B are cross-sectional views illustrating a solar cell including a nanowire array according to an embodiment of the present invention including a nanowire array as a lower electrode.

FIGS. 2A and 2B show the same configuration as FIG. 1A and FIG. 1B except that the nanowire array is used as a lower electrode.

A solar cell including a nanowire array according to an embodiment of the present invention includes a first polarity semiconductor layer 121 and a second polarity semiconductor layer 122 formed on a lower electrode 110, And an upper electrode 140 formed on the semiconductor layers 131 and 132 of the second polarity and the semiconductor layers 131 and 132 of the second polarity,

The lower electrode 110 is a nanowire array including at least one nanowire 111 and 112 and the nanowire array has the same polarity as the first polarity semiconductor layers 121 and 122 directly contacting.

Thus, a solar cell including a nanowire array according to an embodiment of the present invention is characterized in that the nanowire array exhibits an optical effect that reduces the reflection of the surface, and an electrical effect that smoothes the flow of electric current traveling along the surface Therefore, by having the same polarity as that of the first polarity semiconductor layers 121 and 122 to which the nanowire array is directly abutted, the surface resistance can be reduced and the current diffusion can be improved.

In addition, since the solar cell including the nanowire array according to an embodiment of the present invention uses the nanowire array as the lower electrode 110, the scattering effect of light in the nanowire array is strongly generated, The absorption efficiency can be improved.

2A is a cross-sectional view of a solar cell including a nanowire array according to an embodiment of the present invention, wherein the first polarity is p-type and includes a nanowire array as the bottom electrode.

A solar cell including a nanowire array according to an embodiment of the present invention shown in FIG. 2A may have a first polarity of p-type or n-type, and preferably a first polarity of p-type.

2A, a p-type semiconductor layer is used as the first polarity semiconductor layer 121, and a p-type semiconductor layer is used as the second polarity semiconductor layer 131. In the solar cell including the nanowire array according to an embodiment of the present invention, Since the n-type semiconductor layer is used as the n-type semiconductor layer, the lower electrode 110 including the nanowire array including at least one nanowire 111 is the same in polarity as the first polarity semiconductor layer 121, Respectively.

Accordingly, the nanowire array of a solar cell including the nanowire array according to an embodiment of the present invention shown in FIG. 2A may include a p-type nanowire.

According to an embodiment of the present invention, a solar cell including a nanowire array according to an embodiment of the present invention may further include a sub electrode 150 below the lower electrode 110.

The sub electrode 150 may include a metal material and may be formed as a metal mirror under the lower electrode 110 to improve the degree of light convergence of the solar cell and reduce the area and manufacturing cost of the solar cell. have.

FIG. 2B is a cross-sectional view of a solar cell including a nanowire array according to an embodiment of the present invention, wherein the first polarity is n-type and includes a nanowire array at the bottom.

A solar cell including a nanowire array according to an embodiment of the present invention shown in FIG. 2B may have a first polarity of p-type or n-type, and preferably a first polarity of n-type.

2B, an n-type semiconductor layer is used as the first polarity semiconductor layer 122, and a second polarity semiconductor layer 132 is used as the second polarity semiconductor layer 122. In the solar cell including the nanowire array according to an embodiment of the present invention, The lower electrode 110 formed of a nanowire array including at least one nanowire 112 has the same polarity as the first polarity semiconductor layer 122 directly contacting.

Accordingly, the nanowire array of a solar cell including the nanowire array according to an embodiment of the present invention shown in FIG. 2B may include n-type nanowires.

According to an embodiment of the present invention, a solar cell including a nanowire array according to an embodiment of the present invention may further include a sub electrode 150 below the lower electrode 110.

The sub electrode 150 may include a metal material and may be formed as a metal mirror under the lower electrode 110 to improve the degree of light convergence of the solar cell and reduce the area and manufacturing cost of the solar cell. have.

4 is a cross-sectional view of a nanowire having a circular cross-sectional structure.

FIG. 4 illustrates a solar cell including a nanowire array according to an embodiment of the present invention including a nanowire array on the top, but the present invention is not limited thereto, The present invention can be similarly applied to a solar cell including a nanowire array according to an embodiment.

4 illustrates the nanowire 141 having a circular cross section, the cross section of the nanowire 141 may have a polygonal structure such as a triangle, a rectangle, a pentagon, or a hexagon in addition to a circular shape.

Preferably, if the nanowire 141 has a triangular cross-section, the refractive index gradually decreases toward the upper portion, thereby improving the graded index effect that minimizes the reflectance.

A solar cell including a nanowire array according to an embodiment of the present invention can reduce the fill factor of the nanowire as well as the diameter (D) of the nanowire as well as the reflectivity.

4, the space filling ratio of the nanowire 141 can be calculated by dividing the period A of the nanowire 141 by the diameter D of the nanowire 141, ) May be at least 10%.

Since the space filling ratio of the nanowire 141 is 10% or more, the reflectance at the surface can be significantly reduced. In addition, the maximum value of the space filling ratio of the nanowires 141 means a case having a close packed structure.

5A and 5B are flowcharts illustrating a method of manufacturing a solar cell including a nanowire array according to an embodiment of the present invention.

5A and 5B illustrate techniques involving nanowires as top electrodes, but are not limited thereto, and may include nanowire arrays in accordance with a technique including nanowires as lower electrodes, or nanowire arrays in accordance with another embodiment of the present invention Solar cells can also be manufactured in the same way.

A method of fabricating a solar cell including a nanowire array according to an embodiment of the present invention includes forming a first polarity semiconductor layer on a lower electrode (S110), forming a first polarity semiconductor layer on the first polarity semiconductor layer (S120) forming a second polarity semiconductor layer having a different polarity, and transferring an upper electrode (S130) on the second polarity semiconductor layer.

A method of manufacturing a solar cell including a nanowire array according to an embodiment of the present invention includes forming a first polarity semiconductor layer on a lower electrode.

The lower electrode may be formed of a transparent material and may be formed of a transparent conductive oxide (TCO) such as a metal, indium tin oxide (ITO), indium zinc oxide (IZO), aluminum zinc oxide (AZO) or indium zinc tin oxide (IZTO) (Ag), gold (Au), nickel (Ni), titanium (Ti), and chromium (Cr), and the metal may include at least one of a conductive polymer, And the like.

The lower electrode may be a substrate as a lower electrode itself or may be formed on a substrate by chemical vapor deposition (CVD), physical vapor deposition (PVD), sputtering, spin coating, dip coating and drop casting casting, or the like.

The first polarity semiconductor layer may be a p-type semiconductor layer, and the first polarity semiconductor layer may be a Group IV semiconductor such as Si or Ge, a III-V group semiconductor such as InP or GaAs, and at least one of CdS and II-VI , And a dopant of the first polarity may be doped.

When the first polarity is p-type, the dopant of the first polarity is a p-type dopant and may include at least one of Mg, Zn, Ca, Sr, and Ba.

The semiconductor layer of the first polarity may be formed by a method of chemical vapor deposition (CVD), molecular beam epitaxy (MBE), sputtering, and / or vapor phase epitaxy (HVPE).

For example, the semiconductor layer 121 of the first polarity may be formed in the chamber such that the chamber contains a p-type impurity such as trimethyl gallium gas (TMGa), ammonia gas (NH ₃ ), nitrogen gas (N ₂ ), and magnesium Tin cyclopentadienyl magnesium (EtCp2Mg) {Mg (C2H5C5H4) 2} may be implanted to form a p-type GaN layer, but the present invention is not limited thereto.

Then, a second polarity semiconductor layer having a polarity different from the first polarity is formed on the semiconductor layer of the first polarity.

The second polarity semiconductor layer may be an n-type semiconductor layer, and the second polarity semiconductor layer may be a Group IV semiconductor such as Si or Ge, a III-V group semiconductor such as InP or GaAs, and at least one of CdS and II-VI , And a dopant of the second polarity may be doped.

When the second polarity is n-type, the dopant of the second polarity is an n-type dopant and may include at least one of Si, Ge, Sn, Se and Te, but is not limited thereto.

The semiconductor layer of the second polarity may be formed by a method of chemical vapor deposition (CVD), molecular beam epitaxy (MBE), sputtering, and / or vapor phase epitaxy (HVPE).

For example, the semiconductor layer 131 of the second polarity may be formed of a silane containing an n-type impurity such as trimethyl gallium gas (TMGa), ammonia gas (NH ₃ ), nitrogen gas (N ₂ ) Gas (SiH ₄ ) may be implanted to form the n-type GaN layer, but the present invention is not limited thereto.

Finally, the upper electrode is transferred onto the semiconductor layer of the second polarity.

The upper electrode is a nanowire array comprising at least one nanowire and the nanowire array has the same polarity as the second polarity semiconductor layer directly contacting.

The process of transferring the upper electrode will be described in detail with reference to FIG. 5B.

FIG. 5B is a flowchart illustrating a step of transferring an upper electrode in a method of manufacturing a solar cell including a nanowire array according to an embodiment of the present invention.

The step of transferring the upper electrode on the semiconductor layer of the second polarity (S130) comprises the steps of growing (S131) nanowires of the second polarity on the growth substrate, obtaining nanowires of the grown polarity of the second polarity S132) and forming the nanowire array of the second polarity by transferring the obtained second polarity nanowire on the second polarity semiconductor layer (S133).

First, nanowires of the second polarity are grown on the growth substrate.

The growth substrate may include at least one of sapphire, gallium arsenide (GaAs), spinel, silicon (Si), indium phosphide (InP), and silicon carbide (SiC) Lt; / RTI >

A second polarity nanowire array of a solar cell comprising a nanowire array according to an embodiment of the present invention may include n-type nanowires.

The nanowire of the second polarity may be formed of a semiconductor compound including a Group IV semiconductor such as Si and Ge, a III-V semiconductor such as InP or GaAs, and at least one of CdS and II-VI, May be doped.

When the second polarity is n-type, the dopant of the second polarity is an n-type dopant and may include at least one of Si, Ge, Sn, Se and Te, but is not limited thereto.

Preferably, the nanowire of the second polarity is selected from the group consisting of gallium nitride (GaN), aluminum gallium nitride (AlGaN), indium gallium nitride (InGaN) and aluminum indium gallium nitride (AlInGaN) gallium nitride) may be used as the Group III-V semiconductor.

The nanowire of the second polarity may be formed by a chemical vapor deposition (CVD) process, a vapor-liquid-solid process, a thermal chemical vapor deposition (T-CVD) process, A rapid chemical vapor deposition (RTCVD), a plasma enhanced chemical vapor deposition (PECVD), an inductively coupled enhanced chemical vapor deposition (ICPCVD), an organic metal chemical vapor deposition metal-organic chemical vapor deposition (MOCVD), low pressure chemical vapor deposition (LPCVD), catalyst-free MOCVD, atmospheric pressure chemical vapor deposition (APCVD) , Thermal sputtering, thermal or electron beam evaporation, and pulse laser deposition. Can.

For example, when a nanowire of a second polarity is grown by chemical vapor deposition (CVD), a second polarity nanowire may be formed by mounting the growth substrate to a reactor (furnace) 700 to 900), the injected first reaction gas and the second reaction gas may be mixed and grown on the growth substrate.

The first reaction gas and the second reaction gas are precursors for forming the nanowires of the second polarity. When a III-V semiconductor is used as the nanowire of the second polarity, the first reaction gas is a gallium source (Trimethyl Gallium TMGa) and / or Ga metal) may be used, and as the second reaction gas, a Group V reaction gas such as ammonia gas may be used.

For example, if the nanowire of the second polarity is grown in a vapor-liquid-solid method, the nanowire of the second polarity is formed by attaching a growth substrate on which the metal catalyst is deposited to the reactor (furnace) And the reaction gas (the first reaction gas and / or the second reaction gas) is injected at a temperature higher than a specific temperature (for example, 500 to 750), the injected reaction gas is mixed with the metal catalyst to form an alloy When the reaction gas is mixed at a solubility limit or higher, the element contained in the reaction gas can be precipitated in a solid phase and grown on the growth substrate.

When a III-V semiconductor is used as a nanowire of a second polarity, the reaction gas is a gallium source (Trimethyl Gallium (TMGa) and / or Ga metal), and the reaction gas is a precursor for forming a second polarity nanowire. / RTI > and / or ammonia gas may be used.

The metal catalyst may include at least one of gold, silver, aluminum, copper, nickel, palladium, platinum, ruthenium, cobalt and gallium.

 For example, if the nanowire of the second polarity is grown using catalyst-free MOCVD, it is possible to prevent contamination by the catalyst due to the non-use of the catalyst, It is possible to manufacture nanowires having excellent performance.

Thereafter, grown nanowires of the second polarity are obtained.

The diameter of the grown second polarity nanowire may be between 10 nm and 300 nm, the diameter of the at least one nanowire may be between 10 nm and 300 nm, and if the diameter of the at least one nanowire is less than 10 nm, There is a problem in that the surface reflection reduction effect by the nanowire array is not generated. If it exceeds 300 nm, there arises a problem that the back surface scattering effect by the nanowire array occurs, and the surface reflectance is rather increased.

More specifically, if the diameter of the nanowire is larger than the wavelength of light, the reflection characteristic of the light becomes stronger. If the diameter of the nanowire is smaller than the wavelength of light, the reflection characteristic of light is reduced.

For example, when the refractive index of the nanowire is n and the wavelength range that the solar cell can absorb is 300 nm to 1100 nm (based on Si material), the maximum wavelength that the solar cell can absorb is 1100 nm As a rule, the diameter of the nanowire should be less than 1100 / n. Although the refractive index of the Si material changes depending on the wavelength of light, the nanowire 141 preferably has a maximum diameter of 300 nm because the refractive index of the Si material can be about 4 on average.

Further, when fabricating nanowires, it is difficult to reliably manufacture nanowires at a wavelength of 10 nm or less. Therefore, the minimum diameter of the nanowires may be 10 nm, and when the size of the object is less than 10 nm Structure, the maximum diameter of the nanowire is preferably 10 nm.

Further, preferably, the diameter d of the at least one nanowire may be 30 nm to 200 nm. If the diameter d of at least one nanowire deviates from 30 nm to 200 nm, the effect of reducing the surface reflection by the nanowire begins to gradually decrease.

In addition, the nanowires of the grown second polarity may have different widths or lengths.

Finally, the obtained second polarity nanowires are transferred onto the second polarity semiconductor layer to form a nanowire array of the second polarity.

The second polarity nanowires obtained from the growth substrate can be transferred to the first polarity semiconductor layer of the bulk using physical or chemical methods.

Preferably, the second polarity nanowire obtained from the growth substrate is formed by transferring nanowires dispersed in a solvent onto a bulk second semiconductor layer of a polarity using a solution process, and then, at a temperature of about 50 to 150, By drying for 1 minute to 30 minutes, a nanowire array of the second polarity can be formed.

The solvent is selected from the group consisting of deionized water, acetic acid, ethanol, methanol, dichloroethylene, trichlorethylene, chloroform, chlorobenzene, dichlorobenzene, styrene, dimethylformamide, dimethylsulfoxide, xylene, toluene, Propanol, propyl alcohol, tetrahydrofuran, isopropyl alcohol, terpineol, ethylene glycol, diethylene glycol, polyethylene glycol, acetonitrile and acetone.

The nanowire of the second polarity may be formed by at least one of spin coating, physical vapor transport, drop casting, solvent annealing, shear force transfer, and contact printing Lt; / RTI >

Accordingly, a method of fabricating a solar cell including a nanowire array according to an embodiment of the present invention includes growing a nanowire of a second polarity on a growth substrate, and then transferring the nanowire on the bulk of the second polarity semiconductor layer, The etching process for forming the wires can be removed to prevent layer damage and to improve the efficiency of the solar cell.

In addition, the conventional manufacturing method of a bulk solar cell having a thickness of 150 mm or more has a problem in that the production cost is high. However, in the present invention, the nanowire of the second polarity is grown on the growth substrate, The manufacturing cost can be reduced and the efficiency of the solar cell can be improved.

The nanowires of the second polarity of the nanowire array of the second polarity may be regularly arranged or randomly arranged to have a constant period.

The period of the at least one nanowire may be from 10 nm to 300 nm if the nanowires of the second polarity are arranged regularly with a constant period and the nanowires fill the space tightly.

In addition, the process of forming the nanowire array of the second polarity by transferring the nanowires of the second polarity separated from the growth substrate onto the semiconductor layer of the second polarity may be repeated at least one time.

The nanowire arrays of the second polarity may be formed as a single layer or a multilayer, and when the nanowire arrays of the second polarity are formed in multiple layers, the nanowires of the second polarity included in each layer may have different widths or lengths Lt; / RTI >

Accordingly, a method of manufacturing a solar cell including a nanowire array according to an embodiment of the present invention uses a nanowire array of a second polarity including nanowires of a second polarity having different widths or lengths as an upper electrode Thereby reducing surface resistance and improving current diffusion.

6A is an optical microscope image showing a nanowire array of a solar cell including a nanowire array according to an embodiment of the present invention in which the nanowires are randomly arranged.

Referring to FIG. 6A, it can be seen that a silicon nanowire having a p-type polarity having a diameter of 100 nm is well formed on the surface of a silicon substrate having a p-type polarity.

It is also confirmed that the silicon nanowires having the p-type polarity are randomly arranged on the surface of the silicon substrate having the p-type polarity.

6B is an optical microscope image showing a nanowire array of a solar cell including a nanowire array according to an embodiment of the present invention randomly arranged in a specific region only.

Referring to FIG. 6B, it can be seen that the silicon nanowires having the p-type polarity are randomly arranged in the specific region and the silicon nanowires having the p-type polarity are not arranged in another specific region.

6C is an optical microscope image showing a nanowire array of a solar cell including a nanowire array according to an embodiment of the present invention arranged in a multi-layer structure.

Referring to FIG. 6C, it is confirmed that the silicon nanowires having the p-type polarity are randomly arranged in a concentrated manner over several layers.

FIG. 7A is a three-dimensional diagram showing the axis of the nanowire, and FIGS. 7B and 7C are graphs showing the wavelength-reflectance characteristics of a solar cell including a nanowire array according to an embodiment of the present invention.

Referring to FIG. 7A, when light is vertically incident on the nanowire, it can be divided into TE / TM polarized light depending on whether the polarization direction is perpendicular (TE) or parallel (TM) to the nanowire axis, When the axis is parallel, it represents the TM mode polarized light, and when the nanowire axis is vertical, it represents the TE mode polarized light. Also, the reflection characteristic can be changed depending on the polarized light.

FIG. 7B shows the wavelength-reflectance characteristics of a solar cell including a nanowire array according to an embodiment of the present invention with respect to vertically incident TE polarized light, and FIG. The wavelength-reflectance characteristics of a solar cell including a nanowire array according to an embodiment of the present invention are shown.

7B and 7C show the wavelength-reflectance according to the nanowire diameter D when the fill fraction of the nanowire was 30%, 50%, 70% and 100%.

Referring to FIGS. 7B and 7C, it can be seen that both the polarization in the TM mode and the polarization in the TE mode decrease the reflectivity when the fill fraction is above a certain value.

Also, as the width of the nanowire increases, the reflectivity decreases, but when the width of the nanowire is 500 nm, the reflectance is rather increased.

While the invention has been shown and described with reference to certain preferred embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. This is possible.

Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined by the equivalents of the claims, as well as the claims.

110: lower electrode 111, 112: nanowire
121, 122: a first polarity semiconductor layer 131, 132: a second polarity semiconductor layer
140: upper electrode 141, 142: nanowire
150:

Claims (14)

A semiconductor layer of a first polarity formed on the lower electrode;
A semiconductor layer of a second polarity formed on the semiconductor layer of the first polarity and having a polarity different from the polarity of the first polarity; And
And an upper electrode formed on the second polarity semiconductor layer,
/ RTI >
Wherein the lower electrode or the upper electrode is a nanowire array including at least one nanowire and the nanowire array includes a first polarity semiconductor layer or a second polarity semiconductor layer directly contacting the first polarity semiconductor layer, Lt; RTI ID = 0.0 >
The nanowire array is formed in multiple layers,
Wherein the multilayer nanowire array reduces the spatial density of the nanowires of each layer as the distance from the first polarity semiconductor layer or the second polarity semiconductor layer increases so that the refractive index gradually increases from the multi- And a graded index effect in which the reflectance is minimized.
The method according to claim 1,
Wherein the nanowire array increases the light absorption efficiency in the semiconductor layer by reducing surface reflection of incident light or scattering.
The method according to claim 1,
Wherein the nanowire arrays are regularly arranged or randomly arranged to have a constant period.
The method according to claim 1,
Wherein the space filling ratio of the at least one nanowire is 10% or more.
The method according to claim 1,
Wherein the diameter of the at least one nanowire is 10 nm to 300 nm.
delete The method according to claim 1,
Wherein the upper electrode further comprises a sub electrode partially covering the upper electrode.
The method according to claim 1,
And a sub-electrode below the lower electrode.
The method according to claim 1,
Wherein the at least one nanowire comprises at least one of a group IV semiconductor semiconductor, a group III-V group, and a group II-VI semiconductor.
Forming a first polarity semiconductor layer on the lower electrode;
Forming a second polarity semiconductor layer having a polarity different from the first polarity on the first polarity semiconductor layer; And
Transferring the upper electrode onto the second polarity semiconductor layer
Lt; / RTI >
Wherein the upper electrode is a nanowire array comprising at least one nanowire, the nanowire array having the same polarity as the second polarity semiconductor layer directly contacting,
Wherein the step of transitioning the upper electrode on the second polarity semiconductor layer comprises:
Growing a nanowire of a second polarity on a growth substrate;
Obtaining the grown nanowires of the second polarity; And
And transferring the obtained second polarity nanowires onto the second polarity semiconductor layer to form a nanowire array of a second polarity,
The step of transferring the obtained second polarity nanowires onto a second polarity semiconductor layer to form a second polarity nanowire array comprises repeating at least one or more times to transfer the second polarity nanowire array to a multi- Respectively,
Wherein the multilayer second polarity nanowire array reduces the spatial density of the nanowires of each layer as it is further away from the second polarity semiconductor layer so that the refractive index progressively increases from the nanowire array of the second polarity to the top of the nanowire array of the second polarity And a graded index effect in which the reflectance is minimized.
delete delete 11. The method of claim 10,
The second polarity of the nanowire may be formed by a chemical vapor deposition (CVD) method, a vapor-liquid-solid method, a thermal chemical vapor deposition (T-CVD) A rapid thermal chemical vapor deposition (RTCVD), a plasma enhanced chemical vapor deposition (PECVD), an inductively coupled enhanced chemical vapor deposition (ICPCVD), an organic metal chemical vapor deposition (MOCVD), low pressure chemical vapor deposition (LPCVD), catalyst-free MOCVD, atmospheric pressure chemical vapor deposition (APCVD) ), Sputtering, thermal or electron beam evaporation, and pulse laser deposition. Method for manufacturing a solar cell characterized in that the sheet.
11. The method of claim 10,
The second polarity nanowire may be at least one of spin coating, physical vapor transport, drop casting, solvent annealing, shear force transfer, and contact printing. Wherein the transition is carried out by one method.

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