A large-area CZTSSe solar cell and its preparation method

Abstract

The present invention relates to a large-area CZTSSe solar cell and a preparation method thereof. The solar cell comprises an Ag electrode, an ITO / CdS window layer, a CZTSSe absorption layer and a substrate in sequence along the incident light direction, wherein the ITO / CdS window layer is composed of a CdS layer and an ITO layer. The preparation method comprises: (1) cleaning the substrate, then rinsing it with deionized water and drying it with nitrogen to obtain a clean substrate; (2) preparing a CZTSSe precursor film on the clean substrate; selenizing the precursor film with a high-temperature selenization technology to obtain a CZTSSe absorption layer with good crystallinity; (3) depositing a CdS layer and an ITO layer on the CZTSSe absorption layer in sequence by using a chemical water bath deposition method and a magnetron sputtering method; and (4) depositing an Ag electrode on the ITO layer by using a vacuum evaporation technology. The solar cell improves the filling factor of a large-area CZTSSe solar cell device, thereby improving the device performance.

Description

Technical Field

[0001] The invention belongs to the field of thin-film solar cells, and in particular relates to a large-area CZTSSe solar cell and a preparation method thereof. Background Art

[0002] Compared with other thin-film solar cell absorber materials, such as gallium arsenide (GaAs), cadmium telluride (CdTe), copper indium gallium selenide (CIGS), etc., the kesterite-structured CZTSSe is expected to become one of the most promising absorber materials for thin-film solar cells due to its adjustable band gap, rich and inexpensive non-toxic sources of constituent elements, high absorption coefficient, and high carrier concentration. According to the different substrates, it can be divided into rigid and flexible CZTSSe solar cells. At present, the record efficiency of CZTSSe solar cells with molybdenum glass as substrate has reached 13%. In special occasions such as non-planar platforms, building integration, mobile power supplies, and outdoor activities, flexible CZTSSe solar cells have shown great application value due to their soft material, thin thickness, light weight, bendability, high power-to-weight ratio, low energy consumption in the production process, low cost, and easy roll-to-roll large-area continuous production. Among flexible substrates such as polyimide, aluminum foil, molybdenum foil, flexible glass and stainless steel, Mo foil has the advantages of good thermal stability and ductility, sufficient mechanical strength, low resistivity and linear thermal expansion coefficient compatible with CZTSSe materials. It is one of the most excellent substrate materials for flexible CZTSSe devices, and the efficiency of CZTSSe solar cells with flexible Mo foil as substrate has exceeded 11%.

[0003] In the window layer structure (ITO / ZnO / CdS) of the traditional CZTSSe solar cell, the ZnO layer can effectively reduce the leakage caused by the holes in the CdS layer, but its high resistivity and non-ohmic contact with the ITO contact interface will keep the series resistance of the device at a high level, reducing the device performance. Therefore, under the premise of obtaining high-quality CdS film, the new ITO / CdS window layer will effectively reduce the series resistance of the device, simplify the device preparation process, reduce production costs, and shorten the preparation cycle.

[0004] At present, the research on CZTSSe solar cells at home and abroad mainly focuses on small areas (effective area less than 0.5cm 2 ), considering its commercial application, the research of large-area CZTSSe solar cells is necessary. Summary of the invention

[0005] The object of the present invention is to provide a large-area CZTSSe solar cell and a preparation method thereof, wherein the solar cell improves the filling factor of the large-area CZTSSe solar cell device, thereby improving the device performance.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is: a large-area CZTSSe solar cell, which includes an Ag electrode, an ITO / CdS window layer, a CZTSSe absorption layer and a substrate in sequence along the direction of incident light, and the ITO / CdS window layer is composed of a CdS layer and an ITO layer.

[0007] Furthermore, the Ag electrode is a grid electrode with a thickness of 500 to 800 nm.

[0008] Furthermore, the thickness of the CdS layer is 50-80 nm, and the thickness of the ITO layer is 250-300 nm.

[0009] Furthermore, the CZTSSe absorption layer is Cu2ZnSn (S x ,Se 1-x )4 film, thickness is 1.8 ~ 3 μm.

[0010] Furthermore, the substrate is a flexible substrate, and the flexible substrate includes polyimide, flexible glass, aluminum foil, stainless steel, titanium foil and molybdenum foil.

[0011] Furthermore, the effective area of ​​the solar cell exceeds 2 cm 2 .

[0012] The present invention also provides a method for preparing the above-mentioned large-area CZTSSe solar cell, comprising the following steps:

[0013] (1) Clean the substrate, then rinse it with deionized water and blow it dry with nitrogen to obtain a clean substrate;

[0014] (2) Prepare a CZTSSe precursor film on a clean substrate; use high-temperature selenization technology to selenize the precursor film to obtain a CZTSSe absorption layer with good crystallinity;

[0015] (3) Using chemical water bath deposition and magnetron sputtering, a CdS layer and an ITO layer are sequentially deposited on the CZTSSe absorption layer;

[0016] (4) Deposit the Ag electrode on the ITO layer using vacuum evaporation technology.

[0017] Furthermore, in step (2), the preparation method of the CZTSSe precursor film includes a precursor solution method, a sol-gel method, an ink method, a magnetron sputtering method, a doctor blade method, and a pyrolysis spray method.

[0018] Furthermore, in step (4), the pattern of the Ag electrode is determined by a mask, and the area of ​​the Ag electrode does not exceed 10% of the total area of ​​the solar cell.

[0019] Compared with the prior art, the present invention has the following beneficial effects: the large-area CZTSSe solar cell of the present invention has a surface area of ​​more than 2 cm 2 The effective area of ​​CZTSSe solar cells has been greatly reduced, which has promoted the application of CZTSSe solar cells. In addition, the ITO / CdS window layer has a lower resistivity, which reduces the series resistance of the device, simplifies the device preparation process, and shortens the preparation cycle. At the same time, the absorption layer material of the solar cell is rich in sources, green and environmentally friendly, and low in cost, and has the potential for large-scale batch production. In addition, the preparation method of the present invention is simple and easy to realize industrialization. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the structure of a large-area CZTSSe solar cell according to an embodiment of the present invention.

[0021] Figure 2 3 are SEM cross-sectional views of different positions of the absorption layer in the embodiment of the present invention.

[0022] Figure 3 It is the mask pattern of the electrode in the embodiment of the present invention.

[0023] Figure 4 The flexible large-area CZTSSe solar cell in the embodiment of the present invention is different from the device with a traditional window layer. I — V curve. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0025] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0026] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0027] like Figure 1 As shown, this embodiment provides a large-area CZTSSe solar cell, which is composed of an Ag electrode, an ITO / CdS window layer, a CZTSSe absorption layer and a substrate in the direction of incident light, and has an effective area of ​​more than 2 cm 2The conventional window layer structure is ITO / ZnO / CdS, and the window layer structure of the present invention is ITO / CdS, which is composed of a CdS layer and an ITO layer.

[0028] In this embodiment, the Ag electrode is a grid electrode with a thickness of 500 to 800 nm. The thickness of the CdS layer is 50 to 80 nm, and the thickness of the ITO layer is 250 to 300 nm. The CZTSSe absorption layer is a Cu2ZnSn(S x ,Se 1-x )4 film, thickness is 1.8 ~ 3 μm.

[0029] The substrate includes two types: a rigid substrate and a flexible substrate. One is a rigid substrate represented by Mo-plated soda-lime glass, and the other is a bendable flexible substrate including polyimide, flexible glass, aluminum foil, stainless steel, titanium foil, molybdenum foil, etc. In this embodiment, the substrate uses a flexible Mo foil.

[0030] In this embodiment, the preparation process of the large-area CZTSSe solar cell is as follows:

[0031] (1) Processing substrate

[0032] The impurities and oxides on the surface of the Mo foil were treated by electrochemical cleaning technology in a 12.5% ​​sulfuric acid methanol solution, and then ultrasonically cleaned with deionized water, acetone, and anhydrous ethanol for 15 minutes each, and dried with nitrogen. The purity of the Mo foil is 99.998%, the thickness is 0.05 mm ~ 0.1 mm, and the area is 2×2 cm 2 , with bendability;

[0033] (2) Preparation of absorption layer

[0034] The CZTSSe absorption layer with kesterite structure was prepared on the flexible Mo foil by using the precursor solution spin coating method and high temperature selenization technology:

[0035] (201) Five elements, namely copper powder, zinc powder, cadmium powder, tin powder, sulfur powder and selenium powder, were added to a mixture of ethylenediamine and ethylenedithiol in proportion, and the mixture was heated and stirred for 1.5 h. Then, a stabilizer composed of ethanolamine, thioglycolic acid and ethylene glycol methyl ether was added, and the heating and stirring were continued until a uniform and clear CZTSSe precursor solution was obtained.

[0036] (202) In an argon-filled glove box, the CZTSSe precursor solution was coated on a clean Mo foil by spin coating and sintered on a hot plate at 300 °C to obtain a layer of CZTSSe precursor film. The spin coating and sintering process was repeated (9 to 11 times) to obtain a 1.8 to 3 μm thick CZTSSe precursor film.

[0037] (203) The CZTSSe prefabricated layer sample and 0.5 g of selenium powder were placed in a closed graphite box. The graphite box was then placed in a nitrogen-filled rapid thermal annealing furnace and rapidly heated to 550 °C. After maintaining the temperature for 15 min, the box was naturally cooled to obtain a well-crystallized CZTSSe film with a kesterite structure.

[0038] like Figure 2 As shown, the CZTSSe films at six different locations in the sample are composed of large crystal layers and small crystal layers, and their thicknesses are basically the same, which ensures the uniformity of the performance of large-area solar cells.

[0039] (3) Preparation of window layer

[0040] The CdS layer was deposited on the surface of the CZTSSe absorption layer by a chemical water bath method. The deposition time was 15 min at a constant temperature of 75 ℃ to obtain a CdS film with a thickness of 50-80 nm. The ITO layer was deposited on the CdS layer by sputtering. The process parameters were: background vacuum degree <1.0×10 -3 Pa, the sputtering gas is Ar, the working vacuum of the ITO layer is 0.5 Pa, the RF sputtering power is 40 W, the sputtering time is 35 min, and its thickness is 250 ~300 nm;

[0041] (4) Preparation of Ag electrode

[0042] Combined with the large-area battery electrode mask, the Ag electrode is prepared on the window layer using vacuum evaporation technology. The process parameters are: vacuum degree is less than 1×10 -4 Pa, the evaporation rate is 1 Å / s, and the deposition thickness is 500 ~ 800 nm. The Ag electrode area does not exceed 10% of the total solar cell area.

[0043] In this embodiment, a flexible large-area CZTSSe battery with a traditional window layer structure (ITO / ZnO / CdS) was prepared by a similar preparation method for comparison. The other steps are basically the same, except that when preparing the window layer, ZnO / ITO (traditional window layer structure) is deposited on the CdS layer by sputtering. The process parameters are: background vacuum degree <1.0×10 -3 Pa, the sputtering gas is Ar, the working vacuum degree of the ZnO layer is 2 Pa, the RF sputtering power is 80 W, and the sputtering time is 7 min, and a 50-70 nm thick film is obtained. The working vacuum degree of the ITO layer is 0.5 Pa, the RF sputtering power is 40 W, and the sputtering time is 35 min, and its thickness is 250-300 nm.

[0044] Figure 3The mask pattern of the Ag electrode in this embodiment. In the figure: 1-stainless steel plate (20 × 20 × 0.2 mm), 2-marked short line (0.5 × 0.1 mm), 3-main and auxiliary line pattern, 4-main line (15.6 × 0.5 mm), 5-auxiliary line (15.6 × 0.1 mm). Among them, the marked short line is used to determine the battery area, and the main and auxiliary line patterns determine the shape of the Ag electrode. The effective area of ​​the solar cell determined by the mask of this electrode is 2.38 cm 2 .

[0045] like Figure 4 As shown in the figure, the opening voltage of the flexible large-area CZTSSe battery in this embodiment is 0.422 V, the short-circuit current is 76.22 mA, the fill factor is 50.52%, and the photoelectric conversion efficiency is 6.82%. The opening voltage of the flexible large-area CZTSSe battery with a traditional window layer structure is 0.420 V, the short-circuit current is 76.29 mA, the fill factor is 44.35%, and the photoelectric conversion efficiency is 5.97%. Compared with the flexible large-area CZTSSe battery with a traditional window layer structure, the fill factor of the flexible large-area CZTSSe battery of the present invention is greatly improved, thereby significantly improving the photoelectric conversion efficiency of the device by 14.24%.

[0046] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A large-area CZTSSe solar cell, characterized in that: Along the direction of incident light, it includes Ag electrode, ITO / CdS window layer, CZTSSe absorption layer and substrate in sequence, wherein the ITO / CdS window layer is composed of CdS layer and ITO layer; the effective area of ​​the solar cell exceeds 2cm 2 ; The Ag electrode is a grid electrode with a thickness of 500-800 nm; the CdS layer has a thickness of 50-80 nm, and the ITO layer has a thickness of 250-300 nm; the CZTSSe absorption layer is a Cu2ZnSn(S x ,Se 1-x ) 4 thin film, the thickness is 1.8~3μm; the substrate is a flexible substrate, and the flexible substrate is molybdenum foil; The large-area CZTSSe solar cell has an opening voltage of 0.422V, a short-circuit current of 76.22mA, a fill factor of 50.52%, and a photoelectric conversion efficiency of 6.82%; The method for preparing the large-area CZTSSe solar cell comprises the following steps: (1) Processing substrate; The impurities and oxides on the surface of the molybdenum foil were treated by electrochemical cleaning technology in a 12.5% ​​sulfuric acid methanol solution, and then ultrasonically cleaned with deionized water, acetone, and anhydrous ethanol for 15 minutes each, and dried with nitrogen; the purity of the molybdenum foil was 99.998%, the thickness was 0.05mm~0.1mm, and the area was 2×2cm 2 , with bendability; (2) preparing an absorption layer; The CZTSSe absorption layer with zinc stannite structure was prepared on flexible molybdenum foil by using the precursor solution spin coating method and high temperature selenization technology: (201) Copper powder, zinc powder, cadmium powder, tin powder, sulfur powder and selenium powder were added to the mixture of ethylenediamine and ethylenedithiol in proportion, heated and stirred for 1.5 hours, and then a stabilizer composed of ethanolamine, thioglycolic acid and ethylene glycol methyl ether was added, and heating and stirring were continued until a uniform and clear CZTSSe precursor solution was obtained; (202) In an argon-filled glove box, the CZTSSe precursor solution was coated on a clean molybdenum foil by spin coating and sintered on a hot plate at 300 °C to obtain a layer of CZTSSe precursor film. The spin coating and sintering process was repeated 9 to 11 times to obtain a 1.8 to 3 μm thick CZTSSe precursor film. (203) The CZTSSe prefabricated layer sample and 0.5 g of selenium powder were placed in a closed graphite box, and then the graphite box was placed in a nitrogen-filled rapid thermal annealing furnace, and the temperature was rapidly raised to 550 °C. After maintaining for 15 min, it was naturally cooled to obtain a well-crystallized CZTSSe film with a kesterite structure. (3) preparing a window layer; The CdS layer was deposited on the surface of the CZTSSe absorption layer by a chemical water bath method. The deposition time was 15 min at a constant temperature of 75 °C to obtain a CdS film with a thickness of 50-80 nm. The ITO layer was deposited on the CdS layer by magnetron sputtering. The process parameters were: background vacuum <1.0×10 -3 Pa, the sputtering gas is Ar, the working vacuum of the ITO layer is 0.5Pa, the RF sputtering power is 40W, the sputtering time is 35min, and its thickness is 250~300nm; (4) Preparation of Ag electrode; Combined with the large-area battery electrode mask, the Ag electrode is prepared on the window layer using vacuum evaporation technology. The process parameters are: vacuum degree is less than 1×10 -4 Pa, the evaporation rate is 1Å / s, the deposition thickness is 500~800nm; the Ag electrode area does not exceed 10% of the total area of ​​the solar cell.

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