Research On The Stability Of The Solution For Electrodepositing CZTSe Thin Films

Cu₂ZnSnSe₄?CZTS?became one of the most promising solar cell,with the advantage of tolerable band gap,high absorption coefficient,raw materials abundant,low-cost,non-toxic and no resistance.Electrodeposition,which had the advantage of high raw materials utilization and low-cost,was one of the non-vaccum preparation process,and became the important research direction of prepare CZTS solar cell.At recent,the stability of solution and the difficulty to control the composition of precursor were the problems that influented solar cell conversion effiency and limited large scale production.This paper mainly researched on the stability of the Cu-Zn-Sn solution.The analysis of the reaction and electrodeposition mechanism and the experiment verify the stability of the solution that was improved.This paper researched on the stability of the solution and citrate-tartaric and pyrophosphate were chosen as complexing agent.Depending on the theory,when pH was 5,citrate and tartaric complex X into [?Xcit?Tar]⁴-,X=Cu,Zn,Sn,the solution was the most stable.Cyclic voltammograms was applied to analyze the oxidation-reduction and interaction among Cu???,Zn???,Sn???in the mixed solution,and it confirmed the formation of Cu-Zn,Cu-Sn and Zn-Sn oxidation peak.Then,cyclic voltammograms on the Mo substrate had been measured in the solution for one week and the absorbance of the solution were examined by spectrophotometer,which were used to analyze the stability of the two solutions.We came to conclusion that the more citrate concentration the more stable.When pH was 8,pyrophsphate complex with X into chelate,[X?P₂O₇?₂]⁶-,X=Cu,Zn,Sn,which contributed to the stability of the solution.Pyrophosphate solutions were analyzed in same approachs and concluded that the information of Cu-Zn,Zn-Sn oxidation peak.Besidies the solution changed little within three days and it was stable.The experiment was optimized by adding pyrophosphate.The minor changes of maximum absorbance of the solution within 9 days indicated that the stability of the solution was improved.The Cu-Zn-Sn alloy precursors were electrodeposited from the two different solutions.The adhesion of both precursors was excellent.The precursor from pyrophosphate was better than the citrate in the aspect of roughness and compactness.The crystalline phases of both precursors,were Sn and Cu₅Zn₈.After the selenization of two precursors,the CZTS solar cells were prepared,whose conversion efficiency was 4.01%,4.37% respectively.