CAPACITANCE MEASUREMENTS OF CU2S-ZNXCD1-XS SOLAR-CELLS

Capacitance measurements of Cu//2S-Zn//xCd//1// minus //xS solar cells fabricated by vacuum evaporation of ZnS and CdS from an isothermal coaxial source onto metallized glass substrates and by topotaxial formation of Cu//2S in a CuCl dipping solution were obtained in order to investigate the influence of the Zn concentration of the Zn//xCd//1// minus //xS layer on the doping density of Zn//xCd//1// minus //xS and on the space charge and potential distribution of the heterojunction. Zn diffusion from Zn//xCd//1// minus //xS into Cu//2S during the topotaxial formation of the layer and heat treatment of the cells, and Cu diffusion from Cu//2S into Zn//xCd//1// minus //xS during heat treatment of the cells caused a redistribution of the space charge and potential of the heterojunction. The effect of this redistribution and of the density of the interface states on the capacity of the Cu//2S-Zn//xCd//1// minus //xS heterojunction was studied. This study shows that the Zn diffusion into Cu//2S leads to a compensated layer and thus to an enlargement of the band bending in the Cu//2S side.