EFFICIENT PHOTOELECTROCHEMICAL SOLAR-CELLS FROM ELECTROLYTE MODIFICATION

PHOTOELECTROCHEMICAL solar cells (PECs)1-3 have shown energy conversion efficiencies approaching 13% in sunlight4, and up to 15% in simulated insolation5. Of these, only those incorporating n-cadmium chalcogenide electrodes have been demonstrated to be conducive to thin film6 or in situ storage systems7. Previous studies of photoelectrochemical current and voltage limitation2,3,5,8,9 have focused on modification of the semiconductor electrode. Here we take the alternative approach by demonstrating that energy conversion can be improved by prevention of electrode surface modification and by systematic modification of the electrolyte. Electrolyte modification entails investigations of the primary photo-oxidized species, the nature of the counter ion, the distribution of species in solution, and related competing reactions. Optimization of the distribution of species and addition of cyanide to n-CdSe/([KFe(CN)6]2-/3-)aq PECs enhances the available voltage and the ease of charge transfer, and suppresses related decomposition products. The resultant PEC achieves an open-circuit potential of 1.2 V, an efficiency of 16.4% - the highest for any wide-band-gap (1.7 eV) solar cell (solid state or photoelectrochemical) - and a 100-fold improvement in photocurrent lifetime. Each of these represents a step towards realization of a viable PEC. © 1990 Nature Publishing Group.