Electrochemical photovoltaic cells. Project 65021 final technical progress report, April 15, 1979-April 17, 1980

The overall goals of this program have been to experimentally identify semiconductor photoanode/redox couple systems that (a) show promise of meeting acceptable solar efficiencies using polycrystalline materials, and (b) have the potential for use in conjunction with a suitable cathode in which another redox species is available for reduction. Such an overall system allows for the convenient removal, storage, and later discharge of reaction products through the use of porous, flow-through redox electrodes. Increasing solar energy conversion efficiencies and identifying potentially long-life systems were emphasized. Semiconductor/redox couple systems were selected on the basis of the apparent positions of their conduction and valence band energy levels at the interface, together with the semiconductor decomposition potential. Selected redox couples should possess equilibrium potentials that lie negative of the semiconductor decomposition potential and positive of the semiconductor conduction band. Liquid-junction solar cells were characterized using n-MoSe/sub 2/, n-WSe/sub 2/, n-CdSe, and n-GaAs as photoanodes. Results are presented in detail. (WHK