Optical to electrical energy conversion. Characterization of cadmium sulfide and cadmium selenide based photoelectrochemical cells

Abstract

Studies are reported on CS and CdSe based photoelectrochemical cells using aqueous sulfide or polysulfide electrolytes. The key finding is that both n-type CdS and CdSe are stabilized to photoanodic dissolution (irreversible decomposition). The reaction occurring at the photoanode (CdS or CdSe) is the oxidation of the sulfide or polysulfide. But a polysulfide electrolyte undergoes no net chemical change, since the cathode reaction is the reduction of some polysulfide species. The onset of photoresponse for CdSe and CdS based cells is near the band gap of the photoelectrode corresponding to approximately 750 nm for CdSe and approximately 520 nm for CdS. Open circuit photopotentials of up to 0.8 V for CdS and up to 0.65 V for CdSe have been observed in the polysulfide electrolyte. Overall optical to electrical energy conversion of approximately 7% for CdS at 500 nm and approximately 9% for CdSe at 632.8 nm with an output voltage of approximately 0.3 V can be realized at low light intensity. Estimated solar energy conversion efficiency for CdSe is approximately 2%.