Search

CN-122002958-A - Alkali metal doped CdS buffer layer, preparation method and application thereof in preparation of thin film solar cell

CN122002958ACN 122002958 ACN122002958 ACN 122002958ACN-122002958-A

Abstract

The application relates to the technical field of manufacturing of photovoltaic devices, in particular to an alkali metal doped modified CdS buffer layer, a preparation method and application thereof in preparing a thin film solar cell. The alkali metal doped modified CdS buffer layer can be used for effectively doping alkali metal elements into CdS to form intrinsic defects such as gap defects or passivated cadmium vacancies, optimizing the Fermi level position of the CdS buffer layer and improving the energy band alignment between the CdS buffer layer and the thin film solar cell absorption layer, wherein the doped alkali metal comprises at least one of lithium, sodium, potassium, rubidium or cesium, and the doping process can be completed in a chemical water bath deposition or post-treatment step under a low-temperature condition. The thin film solar cell containing the alkali metal doped CdS buffer layer has the advantages that the interface recombination is obviously inhibited, the built-in electric field is improved, the open circuit voltage and the photoelectric conversion efficiency are effectively improved, the process cost is low, and the thin film solar cell is suitable for large-scale production.

Inventors

  • WANG SIYU
  • LIU YUE
  • JIANG ZHENWU

Assignees

  • 天津商业大学

Dates

Publication Date
20260508
Application Date
20260212

Claims (10)

  1. 1. The alkali metal doped CdS buffer layer is characterized by comprising a film of M x Cd 1-x S, wherein 0< x <1, M represents alkali metal elements, the buffer layer is 10nm-100nm, the M x Cd 1-x S is obtained by doping CdS with alkali metal ions, and the metal elements in the alkali metal doping are one or more of lithium, sodium, potassium, rubidium and cesium.
  2. 2. The method for preparing the CdS buffer layer according to claim 1, wherein the preparation method is an in-situ doping chemical water bath deposition method, cadmium-containing compounds and sulfur-containing compounds are subjected to chemical reaction, alkali metal salt is added in the reaction, the temperature is raised to 65-85 ℃ and alkali metal doping is carried out under the constant temperature condition, the CdS buffer layer is prepared into an M x Cd 1-x S film, wherein 0< x <1, M represents alkali metal elements, the thickness of the buffer layer is 10-100 nm, and the elements in the alkali metal doping are one or more of lithium, sodium, potassium, rubidium or cesium.
  3. 3. The method of manufacturing according to claim 2, wherein at least one of the following is satisfied: (1) The cadmium-containing compound is one or more of CdSO 4 、Cd(NO 3 ) 2 、Cd(CH 3 COO) 2 or CdX 2 , wherein X is F, cl, br or I; (2) The sulfur-containing compound is metal sulfide, thiosulfate, thiourea or thioacetamide; (3) The alkali metal salt is sulfate, nitrate, chloride, acetate or hydroxide of alkali metal, the alkali metal is selected from one or more of lithium, sodium, potassium, rubidium or cesium, and the alkali metal salt is preferably KCl, na 2 SO 4 or RbNO 3 .
  4. 4. A production method according to claim 2 or 3, wherein the ratio of the addition amount of the alkali metal ion in the alkali metal salt to the cadmium ion in the cadmium-containing compound is 0.1at.% to 10at.% on a molar concentration basis.
  5. 5. The preparation method of the CdS buffer layer according to claim 1, which is characterized by comprising the following steps of preparing a CdS film by a chemical water bath deposition method or a physical vapor deposition method, immersing the CdS film in an alkali metal salt solution for 10min, and then annealing at 100-300 ℃ for 1-30 min to diffuse alkali metal ions into vacancies or interstitial sites of the CdS film to obtain an alkali metal doped M x Cd 1-x S film.
  6. 6. The method of claim 5, wherein at least one of the following is satisfied: (1) The concentration of the alkali metal salt solution is 0.01M-0.5M; (2) The alkali metal salt solution is a sulfate solution, a nitrate solution, a chloride solution, an acetate solution or a hydroxide solution of alkali metal, and the alkali metal is one or more selected from lithium, sodium, potassium, rubidium or cesium.
  7. 7. Use of an alkali metal doped CdS buffer layer as defined in claim 1 for the preparation of thin film solar cells.
  8. 8. A thin film solar cell comprising a substrate, a bottom electrode, an absorber layer, the alkali metal doped CdS buffer layer of claim 1, a window layer, and a top electrode, laminated in that order.
  9. 9. The thin film solar cell of claim 8, wherein at least one of the following is satisfied: (1) The substrate is soda lime glass, sodium-free glass or quartz glass; (2) The bottom electrode is metal Mo, and the thickness is 1-2 mu m; (3) The absorption layer is a compound of M1, M2, M3 and X or a combination thereof or an antimony selenium sulfur compound semiconductor film, and the thickness is 0.4-3 mu M, wherein M1 is copper, silver or a combination thereof, M2 is indium, zinc or a combination thereof, M3 is gallium, germanium, tin or a combination thereof, and X is selenium, sulfur or a combination thereof; (4) The window layer comprises an intrinsic zinc oxide layer and an aluminum-doped zinc oxide layer which are sequentially arranged, and the thickness of the window layer is 330nm-1650nm; (5) The top electrode is aluminum, nickel aluminum alloy or silver, and the thickness is 0.5-4 mu m.
  10. 10. A method of manufacturing the thin film solar cell according to claim 8 or 9, comprising the steps of: A bottom electrode with a double-layer structure is deposited on the substrate by a magnetron sputtering method, wherein the thickness of the bottom electrode is 1-2 mu m; Preparing a precursor film on the bottom electrode by adopting a sol-gel method, depositing 2 circulating aluminum oxide films on the surface of the precursor film by utilizing an atomic layer deposition technology, and annealing at 550 ℃ for 10min under an X atmosphere to obtain an absorption layer, wherein the X is selenium, sulfur or a combination thereof, and the thickness of the absorption layer is 0.4-3 mu m; Preparing an alkali metal doped CdS buffer layer on the absorber layer according to the method of any one of claims 2-6; Depositing a window layer on the buffer layer by adopting a magnetron sputtering method, wherein the thickness of the window layer is 330nm-1650nm; And depositing a top electrode on the window layer by adopting a thermal evaporation method, wherein the thickness of the top electrode is 0.5-4 mu m.

Description

Alkali metal doped CdS buffer layer, preparation method and application thereof in preparation of thin film solar cell Technical Field The application relates to the technical field of manufacturing of photovoltaic devices, in particular to an alkali metal doped modified CdS buffer layer, a preparation method and application thereof in preparing a thin film solar cell. Background The efficient utilization of renewable energy sources represented by solar energy is an important way for reducing carbon emission in China, and solar cells can directly convert solar radiation into electric energy, so that the method is a core method for achieving the aim. Thin film solar cells, such as copper indium gallium diselenide (CIGS), copper zinc tin sulfur diselenide (CZTSSe) cells, and antimony sulfur selenide, have received much attention due to their high absorption coefficient, high theoretical efficiency, and good stability, however, current solar cells are still limited by carrier recombination problems or insufficient carrier separation and collection capabilities caused by mismatched heterojunction interfaces, and the photoelectric conversion efficiency or stability is still not ideal. Such cells typically employ n-type CdS as a buffer layer. However, conventional Chemical Bath Deposition (CBD) grown CdS thin films typically have a higher intrinsic defect density, such as sulfur vacancies (V S) and cadmium vacancies (V Cd) defects. These defects not only result in CdS self fermi levels being "pinned" with low carrier concentrations and difficult to optimize, but also introduce a large number of interface recombination centers at the CdS/absorber interface. In addition, the Conduction Band Offset (CBO) between CdS and a wide bandgap absorber layer (e.g., CIGS with high Ga content or CZTSSe with high S content) is sometimes too large, forming a "cliff" (cliff) structure, impeding electron transport and exacerbating interfacial recombination. Together, these factors limit the open circuit voltage (V OC) of the cell to well below theoretical. Currently, methods for improving CdS performance mainly include adjusting CBD process parameters, forming (Cd, zn) S using Zn to partially replace Cd, or employing a Cd-free buffer layer (e.g., zn (O, S)). But these methods have limited effectiveness or complex processes or introduce new interface problems. Therefore, the development of the buffer layer modification technology which is simple in process, can effectively improve the carrier concentration of the CdS buffer layer and optimize the heterojunction interface quality of the CdS buffer layer has important significance for breaking through the efficiency bottleneck of the copper-based thin film solar cell. Disclosure of Invention Aiming at the defects existing in the prior art, the application aims to provide an alkali metal doped CdS buffer layer, a preparation method thereof and a thin film solar cell comprising the buffer layer, and by introducing alkali metal elements into CdS crystal lattice, gap defects are formed or vacancy defects of the CdS crystal lattice are effectively passivated, and the energy band structure of the CdS crystal lattice is regulated, so that interface recombination is obviously reduced, and the open-circuit voltage and the overall efficiency of the cell are improved. The first object of the present application is to provide an alkali metal doped CdS buffer layer, the buffer layer is a thin film comprising M xCd1-x S, wherein 0< x <1, M represents an alkali metal element, the buffer layer is 10nm-100nm, M xCd1-x S is obtained by alkali metal ion doping CdS, and the metal element in the alkali metal doping is one or more of lithium (Li), sodium (Na), potassium (K), rubidium (Rb) or cesium (Cs). The second aim of the application is to provide a preparation method of a CdS buffer layer of a thin film solar cell, in particular to an in-situ doped Chemical Bath Deposition (CBD) method, wherein a cadmium-containing compound and a sulfur-containing compound are subjected to chemical reaction, alkali metal salt is added in the reaction, the temperature is raised to 65 ℃ to 85 ℃ and alkali metal doping is carried out under the constant temperature condition, so that the CdS buffer layer is M xCd1-x S film, wherein 0< x <1, M represents alkali metal element, the thickness of the buffer layer is 10nm to 100nm, and the alkali metal doping element is one or more of lithium (Li), sodium (Na), potassium (K), rubidium (Rb) or cesium (Cs). Further, the raw materials are selected to at least satisfy one or more of (1) cadmium-containing compound CdSO 4、Cd(NO3)2、Cd(CH3COO)2 or CdX 2, wherein X is F, cl, br or I, (2) sulfur-containing compound is metal sulfide, thiosulfate, thiourea or thioacetamide, (3) alkali metal salt is sulfate, nitrate, chloride, acetate or hydroxide of alkali metal, wherein the alkali metal is selected from one or more of lithium (Li), sodium (Na), potassium (K), rubidium (Rb) or cesium (Cs