Photochemistry of p-InP saturated CaCl sub 2 solutions.

InP based cells for photoelectrochemical light to electrical energy conversion are critically dependent on the oxidative state of the semiconductor interface. Cr(111)-Cr(11) electrolytes are favorably placed energetically for p-type cells but are lacking in charge transfer kinetics and prone to causing surface passivation by Cr-containing films. Moving from conventional (0.2 M CaCl sub 2) to saturated (5.6 M CaCl sub 2) electrolytes with the p-InP/Cr(111)-Cr(11) semiconductor-electrolyte interface provides a dramatic enhancement in electrochemical output and stability. A combination of ligand bridging acceleration of electron transfer and reduced water activity avoiding passivating Cr oxide films is responsible for these beneficial effects.