Research Of Ag_xCu_1-xSbS₂ Film Prepared By Spray Pyrolysis And Photovoltaic Performance

CuSbS2 is considered as the new next-generation of thin-film solar cell absorber material,due to its earth abundant and environmentally friendly constituents.In recent years,CuSbS2 solar cells have made great progress in the preparative technique and device structure.However,due to the high concentration of defects induced by inevitable unstoichiometric-phase and undesirable band gap structure,the photoelectric conversion efficiency has a big gap compared with the previous-generation of thin film solar cell.Ion substitution is a common method to enhance the quality of crystals.At the same time,ion substitution can also optimize the band structure.Therefore,this work uses cations substitution(Cu partially replaced by Ag)and anion substitution(S partially replaced by Se)to improve the crystal quality of the film.The effect of morphology,band structure,carrier transport,and defect behavior after ion substitution were focused,and the influence of the replacement of Cu by Ag on defect behavior is also analyzed based on density functional theory simulation.1.Select Ag atoms with larger atomic radius and better electron affinity into CuSbS2 crystal structure to preparated the AgxCu1-xSbS2,and control the values of x in the AgxCu1-xSbS2 film by controlling Ag+/(Cu++Ag+)in the spray pyrolysis precursor solution.The spray pyrolysis technology,which can be prepared in a large area,has prepared a single-phase AgxCu1-xSbS2 film with a very close to the ideal chemical ratio.By optimizing the substituted ratio of Ag+/(Cu++Ag+),the PCE was significantly improving the efficiency from 0.73%to 2.48%,and the Ag+/(Cu++Ag+)ratio reaches to 20%with a maximum PCE.Researches have shown that the AgxCu1-xSbS2 film has a larger grain size(300-400 nm)and more compact confocal texture,which are beneficial to carrier transport.The replacement of Cu by Ag atoms reduces the interface transmission resistance and the conduction band offset between AgxCu1-xSbS2 and CdS,so that the AgxCu1-xSbS2 device has fewer recombination centers.At the same time,based on the density functional theory calculation,Ag substitute Cu can increase defect formation energies and passivate anti-defects defects so that AgxCu1-xSbS2 exhibit higher short-circuit current density and more stable crystal structure.2.The element Se of the same group of S is selected for anion substitution,and Se into the CuSbS2 crystal structure to preparated CuSb(S1-xSex)2 through the spray pyrolysis CuSbS2 pre-film selenization treatment,and the Se concentration is controlled by the selenization time.By optimizing the selenization time,compared with the vacuum processing device(0.45%),the selenization 8 min has the highest device efficiency of 0.88%.Studies have shown that the replacement of S by Se can promote the growth of grain size and the film show a compact confocal texture.At the same time,Se substitute S to reduce S vacancy(Vs)and reduce the composite resistance,resulting in a decrease of diode ideality factor A and reverse saturation current density J0,indicating that the CuSb(S1-xSex)2 device has better performance.The special band structure with CuSbS2 near CdS and CuSb(S1-xSex)2 near Au electrode is formed,which reduces the hole barrier between Au electrode and CuSb(S1-xSex)2,as well improves hole collection and transport efficiency.In summary,ion substitution can effectively reduce the concentration of deep-level defects(Cusb,Vs)inside CuSbS2 devices,and significantly improve device performance.At the same time,ion substitution also provides shed light for the study of CuSbS2.