KR101334055B1 - Manufacturing method of chalcogenide solar cell with double texture structure having texture layer and chalcogenide solar cell by the same - Google Patents

Abstract

The present invention relates to a method of manufacturing a chalcogenide-based solar cell having a double texture structure including a texture layer, comprising: preparing a substrate; Forming a texture layer on the substrate; Forming a back electrode on the texture layer; Forming a light absorption layer of chalcogenide-based semiconductor material on the rear electrode; Forming a buffer layer on the light absorbing layer; Forming a transparent electrode on the buffer layer; And forming a front surface texture on the surface of the transparent electrode, wherein the unevenness is formed on the surface of the back electrode by the texture layer.
A chalcogenide-based solar cell having a double texture structure including a texture layer according to the present invention includes a substrate; A texture layer formed on the substrate; A rear electrode formed on the texture layer; A light absorption layer of chalcogenide-based semiconductor material formed on the rear electrode; A buffer layer formed on the light absorption layer; And a transparent electrode formed on the buffer layer, and irregularities are formed on the surface of the rear electrode by a texture structure of the surface of the texture layer, and a front texture structure is formed on the surface of the transparent electrode.
The present invention has a double texture structure of the front texture and the texture layer to greatly increase the light capture performance, thereby improving the photoelectric conversion efficiency of the solar cell.

Description

MANUFACTURING METHOD OF CHALCOGENIDE SOLAR CELL WITH DOUBLE TEXTURE STRUCTURE HAVING TEXTURE LAYER AND CHALCOGENIDE SOLAR CELL BY THE SAME}

The present invention relates to a method for manufacturing a chalcogenide-based solar cell, and more particularly, to a method for manufacturing a chalcogenide-based solar cell having increased efficiency by increasing the light trapping ability including a double texture structure including a texture layer. It is about.

In general, solar cells use diodes composed of p-n junctions and are classified into various types according to the materials used as the light absorbing layer.

Conventionally, solar cells using silicon as the light absorbing layer have become mainstream, but recently, efforts to use various compound semiconductors capable of controlling characteristics as light absorbing layers have been actively performed.

In particular, chalcogenide solar cells, which use direct-transition semiconductors with chalcogenide structures such as CIGS and CZTS, as light absorption layers, are attracting the most attention as materials that can be successfully oxidized in the future.

Chalcogenide means a compound containing chalcogen elements S, Se, and Te, and chalcogenide compounds widely applied in the field of solar cells are composed of group IB-IIIA-VIA elements, CuInS ₂ (CIS), CuGaS ₂ (CGS), CuInSe ₂ (CISe), CuGaSe ₂ (CGSe), CuAlSe ₂ (CASe), CuInTe ₂ (CITe), CuGaTe ₂ (CGTe), Cu (In, Ga) S ₂ (CIGS ), Cu (In, Ga) Se ₂ (CIGSe), Cu ₂ ZnSnS ₄ (CZTS), and the like. Such chalcogenide-based compounds or thin films have a bandgap energy of 1 to 2 eV, which has the best light absorption coefficient (1x10 ⁵ cm ^-1 ) among semiconductors and is very optically stable, making it a very light absorbing layer of solar cells. Ideal material.

Another chalcogenide compound used in the solar cell industry is CdS, which is composed of group IIB-VIA elements, and is suitable as a buffer material located at an interface where PN junctions are formed. Typical chalcogenide-based solar cells use CIGS or CZTS as the light absorption layer and CdS as the buffer layer.

3 is a view showing the structure of a typical CIGS or CZTS solar cell.

In general, a Mo electrode back electrode 30 is formed on the soda-lime glass substrate 10 with the adhesive layer 15 interposed therebetween.

A light absorption layer 40 of CIGS-based or CZTS-based semiconductor material is formed on the rear electrode 30, and a front electrode 60 of TCO material is formed with a buffer layer 50 of CdS material therebetween. Finally, the anti-reflection layer 70 is formed on the front electrode 60.

The present invention is to solve the above-mentioned problems of the prior art, a method for manufacturing a chalcogenide-based solar cell having a double texture structure including a texture layer to improve the light capture performance and the chalcogenide manufactured thereby The purpose is to provide a solar cell.

Method of manufacturing a chalcogenide-based solar cell of a double texture structure comprising a texture layer according to the present invention for achieving the above object comprises the steps of: preparing a substrate; Forming a texture layer on the substrate; Forming a back electrode on the texture layer; Forming a light absorption layer of chalcogenide-based semiconductor material on the rear electrode; Forming a buffer layer on the light absorption layer; Forming a transparent electrode on the buffer layer; And forming a front surface texture on the surface of the transparent electrode, wherein the unevenness is formed on the surface of the back electrode by the texture layer.

The inventors of the present invention invented a method for manufacturing a chalcogenide-based solar cell having improved light trapping ability by forming a texture structure on both sides of the chalcogenide-based light absorbing layer. In particular, since the rear electrode has a thin thickness, a method of forming a texture layer before forming the rear electrode without forming a texture on the rear electrode and forming a rear electrode thereon has invented a method of forming irregularities on the surface of the rear electrode. .

In this case, the step of forming the texture layer is conducted by a heat treatment such that the temperature at which the deposition of a melting point lower metal than the substrate, that the substrate to the melting point of the deposited metal, the heat treatment is O ₂ gas, N ₂ may be carried out in a gas, and O ₂ mixed gas, N ₂ gas atmosphere with a mixed gas selected from air or gas of the inert gas of the inert gas.

In addition, the forming of the texture layer may be performed by depositing metal particles by evaporation or sputtering so that metal particle clusters are formed on the surface, or by applying a metal nanoparticle dispersion and then performing heat treatment to form a metal oxide particle layer or a metal nitride particle layer. Can proceed.

The forming of the front electrode is performed by depositing a TCO by a DC sputtering or an RF sputtering process, and the forming of the front texture is performed by DC sputtering or RF sputtering under conditions that increase the deposited particle energy than forming the front electrode. It is preferable to proceed by.

Using the same equipment, but adjusting the process conditions so that the energy of the deposited particles is higher, the surface roughness becomes rough, thereby forming a texture structure.

On the other hand, the step of forming the front texture may be performed by wet etching the surface of the front electrode by immersion in an acid solution. Since the transparent conductive film used for the front electrode is anisotropically wet etched according to the fine physical density, a texture may be formed on the surface of the front electrode.

The chalcogenide-based solar cell of the double texture structure including the texture layer according to the present invention is characterized by being manufactured by the method described above.

In addition, the chalcogenide-based solar cell having a double texture structure comprising a texture layer according to the present invention, a substrate; A texture layer formed on the substrate; A rear electrode formed on the texture layer; A light absorption layer of chalcogenide-based semiconductor material formed on the rear electrode; A buffer layer formed on the light absorption layer; And a transparent electrode formed on the buffer layer, and irregularities are formed on a surface of the rear electrode by a texture structure of the surface of the texture layer, and a front texture structure is formed on the surface of the transparent electrode.

At this time, the light absorption layer is CuInS ₂ (CIS), CuGaS ₂ (CGS), CuInSe ₂ (CISe), CuGaSe ₂ (CGSe), CuAlSe ₂ (CASe), CuInTe ₂ (CITe), CuGaTe ₂ (CGTe), Cu (In It is preferable that the material is one selected from Ga, S ₂ (CIGS), Cu (In, Ga) Se ₂ (CIGSe), and Cu ₂ ZnSnS ₄ (CZTS).

The present invention configured as described above has a double texture structure of the front texture and the texture layer, thereby greatly increasing the light trapping performance, thereby improving the photoelectric conversion efficiency of the solar cell.

1 is a schematic diagram showing a process of manufacturing a chalcogenide-based solar cell having a double texture structure in accordance with an embodiment of the present invention.
2 is a view showing a light trapping state of the double texture structure chalcogenide solar cell of the present invention.
3 is a view showing the structure of a typical CIGS or CZTS solar cell.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the accompanying drawings, embodiments of the present invention will be described in detail.

1 is a schematic diagram showing a process of manufacturing a chalcogenide-based solar cell of a double texture structure including a texture layer according to an embodiment of the present invention, the manufacturing method of the present embodiment shown in the following order.

The substrate 10 is prepared as shown in FIG. 1A and the surface is cleaned. The type of the substrate is not particularly limited, and materials such as glass, SUS, polymer, and metal may be applied. Recently, soda-lime glass substrates are mainly used in CIGS or CZTS solar cells for improvement of characteristics due to infiltration of Na. However, techniques for diffusing Na by different methods using different substrates have been studied. have.

In the cleaning of the substrate 10, acetone, methanol, and distilled water are generally washed sequentially, and the washing effect may be enhanced by using ultrasonic waves during the washing process.

As shown in FIG. 1B, an adhesive layer 15 is formed on the surface of the substrate 10. The adhesive layer 15 is formed to improve the adhesion between the substrate 10 and the back electrode, and may be omitted according to the type of the substrate 10.

As illustrated in FIG. 1C, the texture layer 20 is formed on the surface of the adhesive layer 15. The texture layer 20 is a layer having a concave-convex texture 22 formed on the surface, and additionally introduces a layer that can easily form a texture structure in place of the substrate or the rear electrode, which is difficult to form the texture structure on the surface. . There are various methods of forming the texture layer 20, and the following method may be applied.

The texture layer 20 may be formed using a metal having a lower melting point than the substrate 10. This method uses the phase change of the metal layer by heating.

A metal having a lower melting point than the substrate 10 is deposited on the surface of the adhesive layer 15 by evaporation or sputtering, and the substrate is heated at a temperature corresponding to the melting point of the deposited metal. The heat treatment process is carried out in an atmosphere of O ₂ , N ₂ , O ₂ / inert gas, N ₂ / inert gas or atmospheric gas, and is carried out for 1 to several tens of minutes under a gas pressure ranging from 1 mTorr to several hundred Torr. When the substrate is heated to a temperature corresponding to the melting point of the deposited metal, the deposited metals are agglomerated with each other as they phase change from a solid to a liquid. A layer can be formed.

Particles agglomerate on the adhesive layer 15 to form a metal layer having an irregular surface can be used as the texture layer 20.

Metal particles having a size of several tens of nm to several micrometers are deposited on the surface of the adhesive layer 15 by evaporation or sputtering, and the texture layer 20 is formed by forming an atmosphere in which the deposited particles aggregate to form an uneven surface. can do.

In the deposition of metal particles, the temperature of the substrate 10 varies depending on the type and particle size of the deposited metal. In general, in order to deposit a smooth and dense thin film, the temperature of the substrate 10 is selectively in the range of 40% or more of the melting point of the metal based on the absolute temperature. Apply. On the contrary, if the temperature of the substrate is controlled to less than 40% of the metal melting point based on absolute temperature while depositing metal particles of several tens of nm to several micrometers, the metal particles cluster together without spreading on the deposited surface at the beginning of deposition. (cluster) can be formed, from which a metal layer having an uneven surface can be deposited.

Metals such as silver or platinum are easily formed to form nano to micro-sized clusters during the deposition process, and a nano structure mask may be used during the deposition process.

Alternatively, the metal nanoparticle dispersion prepared by the metal ion reduction method or the like is applied to the adhesive layer 15 and then heat-treated to form a non-uniform metal oxide particle layer or metal nitride particle layer in nano-micro units to the texture layer 20. It can also be used.

As shown in FIG. 1D, the back electrode 30 is formed on the texture layer 20. Since the rear electrode 30 is thin, it is deposited by the texture 22 on the surface of the texture layer 20 with the unevenness 32 formed on the surface thereof.

CIGS or CZTS solar cells are generally formed with a rear electrode 30 of Mo material. Mo not only has a similar coefficient of thermal expansion to glass used as a substrate for recent CIGS or CZTS solar cells, but also has excellent adhesion and electrical conductivity.

DC sputtering is generally used as a method for forming the back electrode 30 Mo thin film. The DC sputtering process for forming the Mo rear electrode 30 uses a DC voltage of 10 V to several hundred V, flows Ar gas at 1 sccm to several hundred sccm, and performs 1 to 100 minutes at a pressure of 1 mTorr to 100 mTorr. do. DC power is selectively applied in the range of several W to several tens of kW depending on the size of the substrate and target and the spacing between the substrate and the target.

The back electrode 30 may be changed into various configurations such as a double layer of a Na-doped Mo layer and a Na-doped Mo layer according to the type of the substrate 10, and may be used as the back electrode. If so, all configurations may apply. Regardless of the configuration, the rear electrode 30 is thin and is deposited with the unevenness 32 formed on the surface thereof.

As shown in FIG. 1E, a chalcogenide light absorbing layer 40 is formed on the rear electrode 30 having the unevenness 32 formed thereon. In particular, a typical chalcogenide-based material, CIGS-based or CZTS-based semiconductor, is used as the light absorption layer.

The method of forming the CIGS-based or CZTS-based light absorbing layer 40 is largely divided into a vacuum method and a non-vacuum method, and the vacuum method and the non-vacuum method are also divided into various methods, respectively, but are not particularly limited in the present embodiment. Any method that can be deposited on the formed back electrode 30 can be applied.

As shown in FIG. 1F, the buffer layer 50 is formed on the light absorption layer 40. As the buffer layer 50, a CdS thin film is generally applied. The CdS buffer layer 50 is a chemical bath deposition (CBD) method for forming a film by immersing the substrate, which has been advanced to the stage of FIG. 1 (e), in an aqueous solution in which thiourea, cadmium sulfate, and alumina are mixed. Method).

In addition, the buffer layer 50 is a ZnS or ZnSe thin film deposited by a CBD method and an In _x Se _y or ZnIn _x Se _y thin film deposited by a process based on evaporation and a CVD based process. In _x Se _y or ZnSe thin film can be used.

As shown in FIG. 1G, the front electrode 60 is formed on the buffer layer 50. The front electrode 60 deposits a transparent conductive film (TCO) such as ITO, ZnO: Al, ZnO: Ga, and ZnO: B, and these transparent conductive films are generally deposited by DC or RF sputtering, but electron beam evaporation is performed. It can also deposit by other methods, such as a method and a thermal evaporation method.

The process of forming the front electrode 60 by DC or RF sputtering uses DC or RF power density per target area of 0.1 W / cm ² to 2 W / cm ² , and Ar gas or Ar gas at a pressure of 5 mTorr to 100 mTorr. Under a gas mixture of the doping element and 10 minutes to 100 minutes. The gas flow rate for pressure maintenance is selectively applied in the range of 1 sccm to several hundred sccm depending on the volume of the vacuum chamber and the pump capacity, and the total DC or RF power is also applied to the size of the substrate and the target and between the substrate and the target. Depending on the spacing, it is optionally applied in the range of several W to several tens of kW.

In addition, it is possible to change to a variety of configurations, such as forming a transparent conductive film of a double structure by sequentially depositing different types of transparent conductive film, all configurations can be applied as long as it can be used as the front electrode.

As shown in FIG. 1H, the front texture 62 is formed on the front electrode 60. The front texture 62 may be formed by etching the surface of the front electrode 60 to form irregularities and forming a transparent conductive film having irregularities formed on the surface of the front electrode 60.

The method of etching the surface of the front electrode 60 is a method of wet etching with an acid solution such as hydrochloric acid. When the wet etching is performed for several tens to hundreds of seconds by immersing the substrate advanced to the step of FIG. 1 (h) in 0.1 to several% of HCl solution, the surface is unevenly etched due to the difference in the physical strength of the surface of the front electrode 60. This creates a texture on the surface.

The method of additionally forming a transparent conductive film having irregularities on the surface of the front electrode 60 is performed by DC or RF sputtering. The above-described DC or RF sputtering process conditions for forming a transparent electrode focus on forming a thin transparent electrode thin film having a dense structure to act as an electrode. On the other hand, since the front texture 62 is a surface concave-convex structure formed on the sufficiently formed front electrode 60, by controlling the process conditions to adjust the size and energy of the sputtered transparent conductive film particles to form an irregular surface can do.

Specifically, the DC or RF sputtering process for forming the front texture 62 utilizes a DC power density per target area of 2 W / cm ² to 10 W / cm ² , and Ar gas or Ar gas of 0.1 mTorr to 5 mTorr pressure. In the gas conditions in which the doping elements are mixed, it is performed for a relatively short time in the process for forming the front electrode in the range of 1 minute to several tens of minutes. In addition, during the sputtering process, the temperature of the substrate is raised to a range of room temperature to several hundred degrees Celsius.

However, the Ar gas flow rate for pressure maintenance is selectively applied in the range of 1 sccm to several hundred sccm depending on the volume of the vacuum chamber and the pump capacity, and the total DC or RF power is also applied to the size and size of the substrate and target. A range similar to the case of forming the front electrode 60 is applied in that it can be selectively applied in the range of several W to several tens of kW depending on the distance between the targets.

The sputtering process conditions for forming the front texture 62 have higher DC power density per target area, lower gas pressure in the chamber, and higher substrate temperature than the front electrode 60, resulting in the energy of the deposited TCO particles. Is so high that irregularities are formed on the deposition surface. On the other hand, if the energy of the deposited TCO particles is high, the quality of the deposition layer may be degraded, so the sputtering process for forming the front texture 62 is performed relatively short.

Meanwhile, a technique of depositing a transparent electrode layer having its own surface texture on a surface by applying a low pressure CVD (LPCVD) process has been developed, which corresponds to forming a transparent electrode layer and a front surface texture in the present embodiment, respectively. Since it is a technique representing the present invention can be applied to this embodiment.

In addition, a configuration in which a grid electrode made of a metal material such as Al or Ag is added on the front surface texture 62 may be used to improve the performance of the electrode.

As shown in FIG. 1I, an antireflection layer 70 is formed on the front texture 62, and MgF ₂ and Al ₂ O ₃ are generally used as the antireflection layer 70.

An anti-reflection layer 70 of MgF ₂ material is deposited by thermal evaporation using a MgF ₂ pellets or, by using a Mg (thd) ₂ and TiF ₄ as a reaction gas to deposit an atomic layer deposition method (ALD, atomic layer deposition) .

The anti-reflection layer 70 made of Al ₂ O ₃ is deposited by atomic layer deposition using Al (CH ₃ ) ₃ and O ₃ as a reaction gas.

2 is a view showing a light trapping state of a double texture structure chalcogenide-based solar cell including a texture layer of the present invention.

The double-textured chalcogenide-based solar cell manufactured by the steps shown in FIG. 1 is provided with the concave-convex 32 formed on the rear electrode 30 and the front texture 62 formed on the front electrode 60 at the same time.

The solar light incident on the front electrode 60 is reflected on the surface of the rear electrode 30 after photovoltaic generation through the light absorbing layer 40 through the buffer layer 50, and at this time on the unevenness 32 formed on the surface. Diffuse reflection occurs.

Sunlight diffused from the surface of the back electrode 30 having the unevenness 32 performs photovoltaic power through the light absorbing layer 40, and passes through the buffer layer 50 and the front electrode 60, and the front texture 62. In the back is diffusely reflected in the light absorbing layer 40 direction.

While repeating the above process, since the sunlight stays in the light absorption layer 40 for a long time, the efficiency of the solar cell is greatly increased.

While the present invention has been described through the preferred embodiments, the above-described embodiments are merely illustrative of the technical idea of the present invention, and various changes may be made without departing from the technical idea of the present invention. Those of ordinary skill will understand. Therefore, the scope of protection of the present invention should be construed not only in the specific embodiments but also in the scope of claims, and all technical ideas within the scope of the same shall be construed as being included in the scope of the present invention.

10: substrate 15: adhesive layer
20: texture layer 30: rear electrode
40: light absorption layer 50: buffer layer
60: front electrode 62: front texture
70: antireflection layer

Claims (10)

delete Preparing a substrate;
Forming a texture layer on the substrate;
Forming a back electrode on the texture layer;
Forming a light absorption layer of chalcogenide-based semiconductor material on the rear electrode;
Forming a buffer layer on the light absorbing layer;
Forming a transparent electrode on the buffer layer; And
Forming a front surface texture on the surface of the transparent electrode;
The forming of the texture layer may be performed by depositing a metal having a lower melting point than the substrate, and heating the substrate to a temperature corresponding to the melting point of the deposited metal.
The heat treatment is performed in one gas atmosphere selected from O ₂ gas, N ₂ gas, mixed gas of O ₂ and inert gas, mixed gas of N ₂ and inert gas, or atmospheric gas,
The method of manufacturing a chalcogenide-based solar cell having a double texture structure comprising a texture layer, characterized in that irregularities are formed on the surface of the back electrode by the texture layer.
Preparing a substrate;
Forming a texture layer on the substrate;
Forming a back electrode on the texture layer;
Forming a light absorption layer of chalcogenide-based semiconductor material on the rear electrode;
Forming a buffer layer on the light absorbing layer;
Forming a transparent electrode on the buffer layer; And
Forming a front surface texture on the surface of the transparent electrode;
The forming of the texture layer is performed by depositing metal particles by evaporation or sputtering.
The evaporation method or the sputtering is performed in a state in which the temperature of the substrate is less than 40% of the melting point of the metal particles on the basis of absolute temperature, thereby forming metal particle clusters on the surface thereof.
The method of manufacturing a chalcogenide-based solar cell having a double texture structure comprising a texture layer, characterized in that irregularities are formed on the surface of the back electrode by the texture layer.
Preparing a substrate;
Forming a texture layer on the substrate;
Forming a back electrode on the texture layer;
Forming a light absorption layer of chalcogenide-based semiconductor material on the rear electrode;
Forming a buffer layer on the light absorbing layer;
Forming a transparent electrode on the buffer layer; And
Forming a front surface texture on the surface of the transparent electrode;
The forming of the texture layer may include applying a metal nanoparticle dispersion and then performing heat treatment to form a metal oxide particle layer or a metal nitride particle layer.
The method of manufacturing a chalcogenide-based solar cell having a double texture structure comprising a texture layer, characterized in that irregularities are formed on the surface of the back electrode by the texture layer.
The method according to any one of claims 2 to 4,
Forming the transparent electrode proceeds by depositing a TCO in a DC sputtering or RF sputtering process,
The chalcogene of the double texture structure including the texture layer may be formed by DC sputtering or RF sputtering on the condition of increasing the particle energy to be deposited than forming the transparent electrode. Method for manufacturing a nit based solar cell.
The method according to any one of claims 2 to 4,
And forming the front surface texture by wet etching the surface of the transparent electrode by immersing in an acidic solution.
delete delete delete delete

Images