Study On The Preparation And Performance Of ZnO Nanowire Arrays Based On CIGS Solar Cell Trapping Structure

Cu(In,Ga)Se2(CIGS)thin-film solar cell has always been given a lot of attention by virtue of its various advantages like high photoelectric conversion efficiency,high stability,low cost,favorable dim light responsiveness,no photo-induced attenuation effect and flexibility,etc.Moreover,it is the best thin-film solar cell which has been applied in a large scale at present.A buffer layer(i-ZnO layer)with high electrical resistivity is needed between transparent conductive front electrode and light absorbing layer in the CIGS thin-film solar cell.Featuring enormous specific surface area,uneven textured structure and adjustable electrical resistivity,etc,ZnO nanowire array,which is used as buffer layer of CIGS solar cell,can enlarge contact area and accelerate electronic transmission.Furthermore,textured structure of nanowire array can exert light trapping effect and strengthen solar light capture efficiency of the cell so as to further improve the cell's photoelectric conversion efficiency.Preparation technology of ZnO nanowire applied to CIGS solar cell was discussed in this paper.ZnO nanowire arrays were prepared on FTO glass substrate using electrochemical deposition method.Technological parameters like deposition potential,concentration of electro-deposition solution and deposition time were regulated to study their influences on morphologies and properties of ZnO nanowire arrays.Solar cell with FTO/ZnO nanowire arrays/CdS/CIGS/Mo structure was acquired through chemical deposition of CdS layer in water bath and magnetron sputtering of CIGS layer and Mo layer in succession.The cell's photoelectric conversion properties were characterized by testing ?-? curves.The main study results were as follows:(1)Influences of deposition potential on morphologies and properties of ZnO nanowire arrays were studied.Results showed that when cathodic reduction potential U was-1.4V,-1.5V and-1.6V respectively while other technological parameters remained the same,the ZnO nanowire array under-1.5V deposition potential presented hexagonal cylinder with smooth side faces,compact structure and good evenness.(2)ZnO nanowire arrays prepared through electro-deposition method using three-type solutions(concentrations of zinc sources(Zn2+)were 0.0025M/L,0.003M/L and 0.004M/L)were compared.Results showed that the concentration product exceeded Zn(OH)2 solubility-product constant when concentration of zinc source(Zn2+)was 0.004M/L,which would easily result in Zn(OH)2 deposition.When solutions with 0.003M/L and 0.0025M/L concentrations of zinc sources(Zn2+)respectively were used to prepare ZnO nanowire arrays,lengths of nanowire arrays were 300-400nm and 200-300nm respectively,and ZnO nanoarrays generated by the latter contributed more to improvement of photoelectric conversion efficiency of CIGS solar cell.(3)Influences of electro-deposition time on morphologies and properties of ZnO nanowire arrays were studied.Results indicated that morphologies and sizes of ZnO nanowire arrays prepared at different deposition time were different to a certain degree.Length and diameter of the ZnO nanowire array deposited for 20min were 200-300nm and 50nm respectively,conforming to ZnO nano wire array structure needed by CIGS solar cell.(4)Under the optimum processing parameters of the ZnO nanowire array,the deposition potential:-1.5V deposition potential,0.0025M/L solution concentration and 20min deposition time,the obtained photoelectric conversion efficiency of CIGS solar cell is the best.