Comparative study of performance of CdTe, CdSe and CdS thin films-based photoelectrochemical solar cells

Polycrystalline films of CdTe and CdSe were electrodeposited onto titanium substrates from acidic baths, and, polycrystalline CdS thin films were prepared by chemical bath deposition method. Due to surface treatment these films show good photoelectrochemical behaviour in a polysulphide electrolyte with high conversion efficiency and stability. The solid-state parameters of annealed films are calculated and compared with those of unannealed film-based cells. Chemical etching is found to improve short-circuit current and fill-factor whereas photoelectrochemical etching technique improves the stability of photo-anode in polysulphide solution. Annealing promotes incipient fusion of small crystallites and thereby reduces the grain boundaries which are known to act as recombination centres for minority carriers and trapping centres for majority carriers. The conversion efficiency and stability are found to improve by chemical etching of the semiconductor layer because chemical etching pins Fermi level of CdTe, CdSe and Cds photoanodes and promotes exchange current density.