KR20150121748A - Solar cell comprising buffer layer formed by atomic layer deposition and method of fabricating the same - Google Patents

Abstract

The present invention relates to a solar cell and a manufacturing method thereof. The method for manufacturing the solar cell includes the steps of: (a) forming a rear electrode layer on a substrate; (b) forming a light absorption layer on the rear electrode layer; (c) processing the surface of an oxide film of a light absorption layer formed by exposing the light absorption layer with a cleaning solution; (d) forming the buffer layer on the oxide film of the light absorption layer whose surface is processed by an atomic layer deposition method; and (e) forming a front electrode layer on the buffer layer.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a solar cell including a buffer layer formed by atomic layer deposition, and a method of manufacturing the solar cell.

The present invention relates to a solar cell including a buffer layer formed by an atomic layer deposition method and a manufacturing method thereof.

Recently, as a part of the development of new and renewable energy to reduce carbon emissions according to environmental regulations, solar cells that can convert electricity from solar energy into electric energy, which can generate electric power easily, have attracted attention.

Such a solar cell is fabricated using a single crystal or polycrystalline silicon wafer, but monocrystalline silicon is generally used most widely in the field of large-scale power generation systems because of its highest photoelectric conversion efficiency. However, such a monocrystalline silicon is uneconomical because of its complicated manufacturing process and high price.

Accordingly, although a method of manufacturing a solar cell using polycrystalline silicon using a low-grade silicon wafer has been developed although it is relatively inefficient, it is currently being used in power generation systems for residential use. However, this process is also complicated and the price of raw materials is rising due to the recent surge in silicon prices, which limits the cost of manufacturing solar cells.

Accordingly, recently, as a thin film solar cell for overcoming this problem, a method of using amorphous silicon having a multi-junction structure and a method of using a compound semiconductor such as a chalcogenide compound have been developed.

(A) forming a rear electrode layer on a substrate; (b) forming a light absorption layer on the rear electrode layer; (c) treating the surface of the light absorption layer formed by exposing the light absorption layer with a cleaning solution; (d) forming a buffer layer on the surface-treated light absorption layer oxide film by atomic layer deposition; And (e) forming a front electrode layer on the buffer layer.

However, the technical problem to be solved by the present invention is not limited to the above-mentioned problems, and other matters not mentioned can be clearly understood by those skilled in the art from the following description.

(A) forming a rear electrode layer on a substrate; (b) forming a light absorption layer on the rear electrode layer; (c) treating the surface of the light absorption layer formed by exposing the light absorption layer with a cleaning solution; (d) forming a buffer layer on the surface-treated light absorption layer oxide film by atomic layer deposition; And (e) forming a front electrode layer on the buffer layer.

A light absorbing layer in the step (b) is _{CuInS 2 (CIS), CuGaS 2} (CGS), CuInSe 2 (CISe), CuGaSe 2 (CGSe), CuAlSe 2 (CASe), CuInTe 2 (CITe), CuGaTe 2 (CGTe) , At least one chalcogenide compound selected from the group consisting of Cu (In, Ga) S ₂ (CIGS), Cu (In, Ga) Se ₂ (CIGSe), Cu ₂ ZnSnS ₄ have.

In the step (c), the cleaning solution may be at least one selected from the group consisting of NH ₄ OH, HNO ₃ , HCl, H ₂ SO ₄ , NH ₄ F, HF, H ₂ O ₂ , CdSO ₄ , KCN and DI- have.

In the step (c), the cleaning solution may contain at least one selected from the group consisting of NH ₄ OH, HNO ₃ , HCl, H ₂ SO ₄ , NH ₄ F, HF, H ₂ O ₂ , CdSO ₄ , It may be diluted.

The cleaning solution may be diluted 5 to 300 times with DI water.

In the step (c), the treatment of the surface of the light absorption layer oxide film may be performed at a temperature of 25 ° C to 120 ° C.

The O content of the light absorption layer oxide film surface-treated in the step (d) may be 5 at% to 50 at%.

The thickness of the light absorption layer oxide film surface-treated in the step (d) may be 10 nm or less.

In the step (d), the buffer layer may be a Cd-free buffer layer.

In the step (d), the buffer layer may be a layer in which atomic layers of Zn, S, Zn, and O are repeatedly stacked.

In the step (d), the band gap energy of the buffer layer may be 3.2 eV to 3.6 eV.

In the step (d), the thickness of the buffer layer may be 3 nm to 100 nm.

In one embodiment of the present invention, a substrate comprises: a substrate; A rear electrode layer formed on the substrate; A light absorbing layer formed on the rear electrode layer; A buffer layer formed on the light absorption layer by atomic layer deposition; And a front electrode layer formed on the buffer layer, wherein an O content of the surface-treated light absorption layer oxide film formed between the light absorption layer and the buffer layer is 5 at% to 50 at%.

In another embodiment of the present invention, there is provided a lithographic apparatus comprising: a substrate; A rear electrode layer formed on the substrate; A light absorbing layer formed on the rear electrode layer; A buffer layer formed on the light absorption layer by atomic layer deposition; And a front electrode layer formed on the buffer layer, wherein a surface-treated light absorption layer oxide film formed between the light absorption layer and the buffer layer has a thickness of 10 nm or less.

In the solar cell according to the present invention, before the buffer layer is formed by the atomic layer deposition method, the surface of the light absorption layer oxide formed by exposing the light absorption layer is treated with the cleaning solution to completely remove the light absorption layer oxide film, It is possible to maintain the thickness of the oxide film to 10 nm or less, preferably 3 nm or less, to prevent defects in the light absorption layer, to prevent Na from diffusing into the buffer layer, Can be increased.

1 illustrates a method of manufacturing a solar cell including a buffer layer formed by atomic layer deposition according to an embodiment of the present invention.
2 is a schematic cross-sectional view of a solar cell including a buffer layer formed by atomic layer deposition according to an embodiment of the present invention.
FIG. 3 (a) shows the light absorptive layer thickness without the light absorption layer oxide film observed by a bright field transmission electron microscope (BF-TEM), and FIG. 3 (b) (BF-TEM). FIG. 3 (c) shows the thickness of the light absorption layer oxide film surface-treated with the cleaning solution (NH ₄ OH) by a bright field transmission electron microscope (BF-TEM) Respectively.
4 is a graph _showing the results of observation of the surface of a light absorption layer oxide film which has been surface treated with a cleaning solution (NH ₄ OH, HNO ₃ , HF, DI-water) or not surface treated with a scanning electron microscope (SEM) 30k: 30,000 times magnification / 150k: 150,000 times magnification).

The inventors of the present invention confirmed that the photovoltaic conversion efficiency of the solar cell can be finally increased by treating the surface of the light absorption layer oxide film formed by exposing the light absorption layer with a cleaning solution before forming the buffer layer by atomic layer deposition And completed the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art to which the present invention pertains. The present invention may be embodied in many different forms and is not limited to the embodiments described herein.

In order to clearly illustrate the present invention, parts not related to the description are omitted, and the same or similar components are denoted by the same reference numerals throughout the specification.

In the drawings, the thickness is enlarged to clearly represent the layers and regions. In the drawings, for the convenience of explanation, the thicknesses of some layers and regions are exaggerated.

Hereinafter, the formation of an arbitrary structure in the above-mentioned " upper (or lower) " means not only that an arbitrary structure is formed in contact with the upper (or lower) And the present invention is not limited to the configuration including any other configuration.

Hereinafter, the present invention will be described in detail.

(A) forming a rear electrode layer on a substrate; (b) forming a light absorption layer on the rear electrode layer; (c) treating the surface of the light absorption layer formed by exposing the light absorption layer with a cleaning solution; (d) forming a buffer layer on the surface-treated light absorption layer oxide film by atomic layer deposition; And (e) forming a front electrode layer on the buffer layer.

In addition, the present invention provides a semiconductor device comprising a substrate; A rear electrode layer formed on the substrate; A light absorbing layer formed on the rear electrode layer; A buffer layer formed on the light absorption layer by atomic layer deposition; And a front electrode layer formed on the buffer layer, wherein an O content of the surface-treated light absorption layer oxide film formed between the light absorption layer and the buffer layer is 5 at% to 50 at%.

In addition, the present invention provides a semiconductor device comprising a substrate; A rear electrode layer formed on the substrate; A light absorbing layer formed on the rear electrode layer; A buffer layer formed on the light absorption layer by atomic layer deposition; And a front electrode layer formed on the buffer layer, wherein a surface-treated light absorption layer oxide film formed between the light absorption layer and the buffer layer has a thickness of 10 nm or less.

1 illustrates a method of manufacturing a solar cell including a buffer layer formed by atomic layer deposition according to an embodiment of the present invention.

As shown in FIG. 1, a method of manufacturing a solar cell including a buffer layer formed by atomic layer deposition according to an embodiment of the present invention includes the steps of: (a) forming a rear electrode layer on a substrate; (b) forming a light absorption layer on the rear electrode layer; (c) treating the surface of the light absorption layer formed by exposing the light absorption layer with a cleaning solution; (d) forming a buffer layer on the surface-treated light absorption layer oxide film by atomic layer deposition; And (e) forming a front electrode layer on the buffer layer.

2 is a schematic cross-sectional view of a solar cell including a buffer layer formed by atomic layer deposition according to an embodiment of the present invention.

As shown in FIG. 2, a solar cell 1 including a buffer layer formed by atomic layer deposition according to an embodiment of the present invention includes a substrate 10; A rear electrode layer (20) formed on the substrate (10); A light absorbing layer 30 formed on the rear electrode layer 20; A buffer layer 40 formed on the light absorption layer 30 by atomic layer deposition; A front electrode layer 50 formed on the buffer layer 40; And a surface-treated light absorbing layer oxide film 35 'formed between the light absorbing layer 30 and the buffer layer 40 and having an O content of 5 at% to 50 at% or a thickness of 10 nm or less, ).

(a): On the substrate 10 The rear electrode layer 20  formation

In the present invention, step (a) is a step of forming the rear electrode layer 20 on the substrate 10.

The substrate 10 may be a glass substrate, a ceramic substrate, a metal substrate, or a polymer substrate.

For example, as the glass substrate, soda lime glass or high strained pointsoda glass substrate can be used. As the metal substrate, a substrate including stainless steel or titanium can be used. As the substrate, a polyimide substrate can be used.

The substrate 10 may be transparent. The substrate 10 may be rigid or flexible.

The rear electrode layer 20 is formed on the substrate 10 and may include a metal such as Mo as a conductive layer.

The rear electrode layer 20 may be a single layer or a plurality of layers of two or more layers. When the back electrode layer 20 is formed of a plurality of layers of two or more layers, the respective layers may be formed of the same metal or may be formed of different metals.

The formation of the rear electrode layer 20 may be performed by one or more known methods selected from the group consisting of sputtering, vacuum evaporation, chemical vapor deposition, atomic layer deposition, ion beam deposition, screen printing, spray dip coating, .

The thickness of the rear electrode layer 20 is preferably 0.1 to 1 占 퐉, more preferably 0.5 占 퐉, but is not limited thereto.

(b): The light absorbing layer 30  formation

The light absorbing layer 30 may be formed on the rear electrode layer 20 by depositing and annealing the light absorbing layer material on the rear electrode layer 20, .

The light absorption layer 30 may be formed of a material having a light absorption layer such as 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 CdTe. But is not limited thereto.

The deposition of the light absorbing layer material may be performed by vacuum deposition or may be performed by non-vacuum deposition. Specifically, the deposition of the light absorption layer material may be performed by vacuum deposition, and may be performed by one or more methods selected from the group consisting of sputtering, vacuum evaporation, chemical vapor deposition, atomic layer deposition and ion beam deposition, Deposition is by non-vacuum deposition and may be by one or more methods selected from the group consisting of screen printing, spray dip coating, tape gelling and ink jet.

The heat treatment may occur simultaneously with the deposition of the light absorbing layer material, and may occur after the deposition of the light absorbing layer material.

Also, the heat treatment may be performed in an atmosphere of Se or S, and the heat treatment may be performed at 300 ° C to 600 ° C for 30 minutes to 1 hour.

For example, precursors of Cu, In, Ga and Se are deposited by a sputtering method and selenized by heat treatment using H ₂ Se or H ₂ S gas in a heat treatment chamber to form Cu (In, Ga ) S ₂ (CIGS) chalcogenide-based compound may be formed, or a crucible containing a Cu, In, Ga, or Se source in a solid form may be heated and heat- by evaporation in the atmosphere at the same time it may form the light absorption layer 30 including a Cu (in, Ga) S ₂ (CIGS), a chalcogenide-based compound.

(c): The light absorbing layer Oxide film (35) surface is treated with a cleaning solution

In the present invention, step (c) is a step of treating the surface of the light absorption layer oxide film 35 formed by exposing the light absorption layer with a cleaning solution.

The entire surface of the light absorbing layer oxide film 35 can be removed by treating the surface of the light absorbing layer oxide film 35 with a cleaning solution and the thickness of the light absorbing layer oxide film 35 ' May be kept at 3 nm or less. At this time, if the thickness of the surface-treated light absorbing layer oxide film 35 'exceeds the above range, defects of the light absorbing layer 30 occur, and it is impossible to prevent Na from diffusing into the buffer layer 40 .

Before the buffer layer 40 is formed by atomic layer deposition, which is a kind of dry method, the light absorption layer 30 is exposed to the outside air such as atomic layer deposition (ALD) oxidizing agent, H ₂ O, H ₂ O ₂ , O ₃ , The formation of the oxide film 35 is inevitable. The surface of the light absorbing layer oxide film 35 is treated with the cleaning solution to completely remove the light absorbing layer oxide film 35 or to maintain the thickness of the light absorbing layer oxide film 35 ' It is possible to prevent defects of the light absorption layer 30 and to prevent Na from diffusing into the buffer layer 40.

The surface of the light absorbing layer oxide film 35 is treated with a cleaning solution. The cleaning solution may be prepared by removing the light absorbing layer oxide film 35 entirely or by subjecting the surface-treated light absorbing layer oxide film 35 'to a thickness of 10 nm or less, The surface of the light absorption layer oxide film 35 'is etched at a specific etching rate so that the thickness of the oxide film 35'

The cleaning solution may be at least one selected from the group consisting of NH ₄ OH, HNO ₃ , HCl, H ₂ SO ₄ , NH ₄ F, HF, H ₂ O ₂ , CdSO ₄ , KCN and DI-water.

The cleaning solution is H ₂ O ₂ Or DI-water, it is not used as an etching solution but is used as a surface cleaning solution. Specifically, the light absorbing layer 30 is exposed to form a Na-O complex or a Na-Se-O complex on the surface of the light absorption layer oxide film 35, which is washed with H ₂ O ₂ or DI-water. Specifically, the cleaning solution may be prepared by diluting one or more selected from the group consisting of NH ₄ OH, HNO ₃ , HCl, H ₂ SO ₄ , NH ₄ F, HF, H ₂ O ₂ , CdSO ₄ and KCN in DI water And at least one selected from the group consisting of NH ₄ OH, HNO ₃ and CdSO ₄ is diluted in DI water, or a solution in which NH ₄ F is diluted in DI water and a solution in which HF is diluted in DI water (Buffered Oxide Etchant) mixed at a certain ratio. However, the present invention is not limited thereto.

In particular, in the case of BOE (Buffered Oxide Etchant), HF is directly involved in the treatment of the light absorption layer oxide film 35 and NH ₄ F serves as a buffer solution for improving the etching uniformity by adjusting the etching rate. At this time, the cleaning solution may be diluted 5 to 300 times with DI water.

The treatment of the surface of the light absorption layer oxide film 35 may be performed at a temperature ranging from 25 ° C to 120 ° C, but is not limited thereto. At this time, when the treatment of the surface of the light absorbing layer oxide film 35 is performed at a temperature lower than 25 ° C, the light absorbing layer oxide film 35 is not etched due to a reactivity failure between the cleaning solution and the light absorbing layer oxide film 35, When the treatment of the surface of the light absorbing layer oxide film 35 is performed at a temperature exceeding 120 캜, the light absorbing layer oxide film 35 and the light absorbing layer 30 The thickness of the light absorbing layer 30 is reduced and the composition of the light absorbing layer is changed, thereby deteriorating the performance of the solar cell.

The cleaning solution was H ₂ SO ₄ Or H ₂ O ₂ is preferably carried out at a temperature of 90 ° C to 120 ° C, but is not limited thereto.

The treatment of the surface of the light absorbing layer oxide film 35 may be performed once or the treatment of the surface of the light absorbing layer oxide film 35 and the formation of the buffer layer 40 may be carried out alternately.

The O-content of the surface-treated light absorbing layer oxide film 35 'is preferably 5 at% to 50 at%, but is not limited thereto. At this time, by maintaining the O content of the surface-treated light absorption layer oxide film 35 'within the above range, defects of the light absorption layer are prevented, Na is prevented from diffusing into the buffer layer, shunt path is reduced, The series resistance of the battery is reduced to prevent the decrease in efficiency due to the formation of the light absorption layer oxide film 35. [

The surface-treated light absorption layer oxide film 35 'having an O content of 5 at% to 50 at% is subjected to XPS (X-ray photoelectron spectroscopy) and AES (Augar electron spectroscopy). Specifically, when the surface-treated light absorption layer oxide film 35 'is formed, the SeO ₂ peak area on the binding energy [eV] increases and the Se-Se peak area , And the Auger kinetic energy [eV] phase Cu peak shifts toward the higher binding energy direction.

(d): The buffer layer 40 Atomic layer  Formation by evaporation

In the step (d) of the present invention, the buffer layer 40 is formed on the surface-treated light absorption layer oxide film 35 'by atomic layer deposition.

The buffer layer 40 is formed on the surface-treated light absorption layer oxide film 35 'and may be formed of at least one layer. At this time, the buffer layer 40 is an n-type semiconductor layer, and the light absorbing layer is a p-type semiconductor layer. Therefore, the light absorbing layer 30 and the buffer layer 40 form a pn junction. Since the light absorption layer 30 and the front electrode layer 50 have a large difference in lattice constant and energy band gap, a good junction can be formed by inserting the buffer layer 40 having a band gap in the middle of the two materials .

Conventionally, the buffer layer 40 is mainly formed of CdS or the like by chemical solution deposition (CBD), which causes contamination, which is problematic from the environmental viewpoint.

Thus, the present invention solves the conventional problem by using a Cd-free buffer layer formed by atomic layer deposition (ALD) on the surface-treated light absorption layer oxide film 35 'as the buffer layer 40 .

The surface treatment of the light absorption layer oxide film 35 minimizes the thickness of the surface-treated light absorption layer oxide film 35 'to improve the surface characteristics of the light absorption layer 30. The buffer layer 40 formed thereon has a composition, , Growth rate, and so on.

The buffer layer 40 may be a Cd-free buffer layer, but is not limited thereto. That is, the Cd-free buffer layer refers to a buffer layer that does not contain cadmium so that an eco-friendly process can be performed without being subjected to environmental regulations.

When the Cd-free buffer layer contains Zn (O, S) in the buffer layer 40, atomic layers of Zn, S, Zn, and O may be repeatedly formed by atomic layer deposition. At this time, the molar ratio of O: S in the buffer layer may be 3: 1 to 10: 1.

The band gap energy of the buffer layer 40 is preferably 3.2 eV to 3.6 eV, more preferably 3.25 eV to 3.55 eV, but is not limited thereto. When the buffer layer 40 contains only the ZnO composition, the band gap energy is 3.2 eV. When the buffer layer 40 contains only the ZnS composition, the band gap energy is 3.6 eV. By adjusting the molar ratio, the band gap energy of the above range can be obtained.

The thickness of the buffer layer 40 is preferably 3 nm to 100 nm, more preferably 3 nm to 50 nm, but is not limited thereto. At this time, if the thickness of the buffer layer 40 is less than the above range, the buffer layer 40 is not uniformly formed, and a portion where the front electrode layer 50 contacts the light absorbing layer 30 is generated, If the thickness of the buffer layer 40 is more than the above range, the transmittance of the buffer layer 40 is reduced, and the amount of light entering the light absorbing layer 30 is reduced to reduce the light conversion efficiency. In particular, by forming the buffer layer 40 to have a thickness of 50 nm or less, there is an improvement in throughput and a capacity-up effect in the manufacturing process.

(e): The front electrode layer 50  formation

The front electrode layer 50 is formed on the buffer layer 40. The front electrode layer 50 is a window layer forming a pn junction with the light absorbing layer and may be formed of ZnO, Or ZnO doped with alumina (Al ₂ O ₃ ), ITO, or the like.

The front electrode layer 50 may have a double structure in which an n-type ZnO thin film or an ITO (Indium Tin Oxide) thin film is deposited on the i-type ZnO thin film with excellent electro-optical characteristics.

The thickness of the i-type ZnO thin film is preferably 10 nm to 70 nm, more preferably 40 nm to 50 nm, but is not limited thereto. The thickness of the n-type ZnO thin film or ITO (Indium Tin Oxide) thin film is preferably 250 nm to 1000 nm, more preferably 500 nm to 1000 nm, but is not limited thereto.

At this time, since the i-type ZnO thin film functions as a transparent electrode on the entire surface of the solar cell 1, it is preferable that the i-type ZnO thin film has high light transmittance and good electric conductivity and is formed of undoped ZnO thin film. In addition, the n-type ZnO thin film deposited on the i-type ZnO thin film has a low resistance value by doping ZnO with aluminum (Al) or alumina (Al ₂ O ₃ ), and the production cost relative to ITO (Indium Tin Oxide) There is an economical advantage because it is low.

The solar cell 1 according to the present invention is characterized in that before the buffer layer 40 is formed by atomic layer deposition, the surface of the light absorption layer oxide film 35 formed by exposing the light absorption layer is treated with a cleaning solution, It is possible to keep the thickness of the absorption layer oxide film 35 'at 10 nm or less, preferably 3 nm or less, to prevent defects of the light absorbing layer 30 and to prevent Na from diffusing into the buffer layer 40 So that the performance of the solar cell 1 can be improved and the photoelectric conversion efficiency of the solar cell 1 can be increased.

Hereinafter, preferred embodiments of the present invention will be described in order to facilitate understanding of the present invention. However, the following examples are provided only for the purpose of easier understanding of the present invention, and the present invention is not limited by the following examples.

[ Example ]

Example  One

A Mo-based alloy formed on a sodalime glass substrate was coated by a DC sputtering method to form a 0.5 μm rear electrode layer. Cu, In, Ga, and Se precursors were deposited on the back electrode layer by DC sputtering method and then heat-treated at 550 ° C for 30 to 60 minutes in an atmosphere of Se to form a light absorbing layer containing a CIGS compound of 2 μm. Then, the light absorbing layer is exposed to the outside air to form a light absorbing layer oxide film. The surface of the light absorbing layer oxide film is irradiated with a cleaning solution of NH ₄ OH diluted 5 to 300 times with DI water at 25 to 120 ° C at a rate of 10 Å / min (5 times dilution: 25 占 폚, 1 minute, 300 times dilution: 120 占 폚, 30 minutes). A Zn (O, S) buffer layer of 40 nm was formed on the oxide layer of the light absorption layer by atomic layer deposition and then coated by RF sputtering to form an i-type ZnO thin film of 50 nm and an n-type ZnO thin film of 1000 nm to form a front electrode layer The solar cell was finally manufactured.

Example  2

Except that the HNO ₃ cleaning solution diluted 5 to 300 times with DI water was supplied and etched at 25 to 120 ° C at an etching rate of 30 Å / min or more.

Example  3

Except that the HCl cleaning solution diluted 5 to 300 times with DI water was supplied and etched at an etching rate of 30 Å / min or more at 25 to 120 ° C.

Example  4

Except that the H ₂ SO ₄ cleaning solution diluted 5 to 300 times with DI water was supplied and etched at an etching rate of 10 Å / min at 25 to 120 ° C.

Example  5

Except that an HF cleaning solution diluted 5 to 300 times with DI water was supplied and etched at an etching rate of 15 Å / min at 25 to 120 ° C.

Example  6

Except that the H ₂ O ₂ cleaning solution diluted to 5 to 300 times with DI water was supplied and the surface treatment was performed at 25 to 120 ° C.

Example  7

Except that the DI-water cleaning solution was supplied and the surface treatment was performed at 25 to 120 ° C.

Example  8

Except that NH ₄ OH and CdSO ₄ mixed diluted solutions diluted 5 to 300 times with DI water were supplied and etched at an etching rate of 10 Å / min at 25 to 120 ° C.

Example  9

Except that KCN cleaning solution diluted 5 to 300 times with DI water was supplied and etched at 25 to 120 ° C at an etching rate of 30 Å / min or more.

Comparative Example  One

Except that the surface of the light absorption layer oxide film was not treated with the cleaning solution at all.

Experimental Example

(One) The light absorbing layer Oxide film  Thickness measurement

The thickness of the light absorbing layer oxide film surface-treated according to Examples 1 to 9 and the thickness of the light absorbing layer oxide film not subjected to the surface treatment according to Comparative Example 1 were observed with a bright field transmission electron microscope (BF-TEM) 1 and Fig.

division Thickness (nm) Example 1 <3 nm Example 2 <3 nm Example 3 <3 nm Example 4 <3 nm Example 5 <3 nm Example 6 10 nm Example 7 10 nm Example 8 <3 nm Example 9 <3 nm Comparative Example 1 15 nm

3 (a) shows the light absorptive layer thickness not formed with the light absorption layer oxide film observed with a bright field transmission electron microscope (BF-TEM), and FIG. 3 (b) 3 (c) shows the thickness of the light absorption layer oxide film surface-treated according to Example 1 under a bright field transmission electron microscope (&quot; BF-TEM).

As shown in Table 1 and FIG. 3, in Examples 1 to 9, it was confirmed that the thickness of the light absorption layer oxide film was smaller than that of Comparative Example 1. In Examples 1 to 5 and 8 to 9, It was confirmed that the thickness of the film was very small, < 3 nm.

(2) The light-  Evaluation of surface characteristics

Surface characteristics of the light absorption layer oxide films prepared according to Examples 1, 2, 5 and 7 and Comparative Example 1 were observed by a scanning electron microscope (SEM), and the results are shown in FIG.

As shown in FIG. 4, it was confirmed that the surface characteristics of the light absorption layer oxide film were significantly improved in Examples 1, 2, 5, and 7 as compared with Comparative Example 1.

 (3) Evaluation of solar cell performance and photoelectric conversion efficiency

The open circuit voltage (V _oc ), the short circuit current density (J _sc ), the charge factor (FF) and the photoelectric conversion efficiency (η) of the solar cell manufactured according to Examples 1 to 9 and Comparative Example 1 were evaluated, Table 2 shows the results.

division V _oc
(mV) J _sc
(mA / cm 2) FF
(%) η
(%) Example 1 585 32.8 63 12.1 Example 2 613 33.4 64 13.1 Example 3 599 32.8 59 11.6 Example 4 600 33.1 56 11.1 Example 5 628 33.4 67 14.1 Example 6 630 28 55 9.7 Example 7 630 28 60 10.6 Example 8 620 34.2 66.5 14.1 Example 9 620 33.5 68 14.1 Comparative Example 1 630 30 35 6.6

As shown in Table 2, in the case of Examples 1 to 5 and 8 to 9, the short circuit current density (J _sc ), the charging factor (FF) and the photoelectric conversion efficiency The short-circuit current density (J _sc ) of the solar cell was lower than that of Comparative Example 1, but the charge factor (FF) and the photoelectric conversion efficiency (η) were both high in Examples 6 to 7 .

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (14)

(a) forming a rear electrode layer on a substrate;
(b) forming a light absorption layer on the rear electrode layer;
(c) treating the surface of the light absorption layer formed by exposing the light absorption layer with a cleaning solution;
(d) forming a buffer layer on the surface-treated light absorption layer oxide film by atomic layer deposition; And
(e) forming a front electrode layer on the buffer layer
A method of manufacturing a solar cell.
The method according to claim 1,
A light absorbing layer in the step (b) is _{CuInS 2 (CIS), CuGaS 2} (CGS), CuInSe 2 (CISe), CuGaSe 2 (CGSe), CuAlSe 2 (CASe), CuInTe 2 (CITe), CuGaTe 2 (CGTe) , At least one chalcogenide compound selected from the group consisting of Cu (In, Ga) S ₂ (CIGS), Cu (In, Ga) Se ₂ (CIGSe), Cu ₂ ZnSnS ₄
A method of manufacturing a solar cell.
The method according to claim 1,
In the step (c), the cleaning solution is at least one selected from the group consisting of NH ₄ OH, HNO ₃ , HCl, H ₂ SO ₄ , NH ₄ F, HF, H ₂ O ₂ , CdSO ₄ , KCN and DI-
A method of manufacturing a solar cell.
The method according to claim 1,
In the step (c), the cleaning solution may contain at least one selected from the group consisting of NH ₄ OH, HNO ₃ , HCl, H ₂ SO ₄ , NH ₄ F, HF, H ₂ O ₂ , CdSO ₄ , Diluted
A method of manufacturing a solar cell.
5. The method of claim 4,
The cleaning solution was diluted 5-fold to 300-fold with DI-water
A method of manufacturing a solar cell.
The method according to claim 1,
In the step (c), the treatment of the surface of the light absorption layer oxide film is performed at a temperature of 25 ° C to 120 ° C
A method of manufacturing a solar cell.
The method according to claim 1,
The O-content of the light-absorbing layer oxide film surface-treated in the step (d) is preferably 5 at% to 50 at%
A method of manufacturing a solar cell.
The method according to claim 1,
The thickness of the light absorption layer oxide film surface-treated in the step (d) is preferably 10 nm or less
A method of manufacturing a solar cell.
The method according to claim 1,
In the step (d), the buffer layer is a Cd-free buffer layer
A method of manufacturing a solar cell.
The method according to claim 1,
In the step (d), the buffer layer is formed by repeatedly laminating atomic layers of Zn, S, Zn and O
A method of manufacturing a solar cell.
The method according to claim 1,
In the step (d), the band gap energy of the buffer layer is 3.2 eV to 3.6 eV
A method of manufacturing a solar cell.
The method according to claim 1,
In the step (d), the thickness of the buffer layer is 3 nm to 100 nm
A method of manufacturing a solar cell.
Board;
A rear electrode layer formed on the substrate;
A light absorbing layer formed on the rear electrode layer;
A buffer layer formed on the light absorption layer by atomic layer deposition; And
And a front electrode layer formed on the buffer layer,
The O-content of the surface-treated light absorption layer oxide film formed between the light absorption layer and the buffer layer is 5 at% to 50 at%
Solar cells.
Board;
A rear electrode layer formed on the substrate;
A light absorbing layer formed on the rear electrode layer;
A buffer layer formed on the light absorption layer by atomic layer deposition; And
And a front electrode layer formed on the buffer layer,
Wherein a thickness of the surface-treated light absorption layer oxide film formed between the light absorption layer and the buffer layer is 10 nm or less
Solar cells.

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