EFFECT OF CdCl2 TREATMENT CONDITIONS ON THE DEEP LEVEL DENSITY,CARRIER LIFETIME AND CONVERSION EFFICIENCY OF CdTe THIN FILM SOLAR CELLS

摘要

The effect of CdCl2 annealing conditions of glass/TCO/n-CdS/p-CdTe solar cell structures on the deep level density and carrier lifetime of the p-CdTe layer and correlation with the solar cell conversion efficiency was investigated.CdCl2.treatment was carried out at temperatures ranging from 370 to 460°C for 15 min.A clear correlation between trap density,carrier lifetime,conversion efficiency and the CdCl2 annealing conditions was observed.Un-annealed structures had a conversion efficiency of 5.7%,hole trap energy of Ev+0.42eV,hole trap density of 8.71x10~(14)cm~(-3),and decay lifetime of 0.15mu s.The optimum CdCl2 annealing temperature was found to be 415°C for structures grown at a substrate temperature of 595°C,where the conversion efficiency,hole trap energy,hole trap density,decay lifetime were 13.4%,Ev+0.44eV,8.10x10~(12) cm~(-3) and 0.40 mu s,respectively.