598 J . EZectrochem . Soc : ELECTROCHEMICAL SCIENCE AND TECHNOLOGY April

The photoelec t rochemical behavior of n and p I n P single crys taI semiconductors was inves t iga ted in acetoni t r i le (ACN) solutions which contained var ious e lect roact ive compounds. The cyclic vo l t ammograms of the semiconductors in the d a r k and i l lumina ted wi th red l ight were compared to the Nerns t ian behavior at a P t d isk electrode. The ex ten t of photodissolut ion of the semiconductors was decreased in ACN compared to aqueous solutions at s imi lar potentials . In t e rmed ia te levels or surface states located be tween the conduct ion band and valence band which media te e lect ron t ransfe r wi th solut ion redox couples a re proposed. An underpo ten t ia l was developed for the photo assisted oxidat ions and reduct ions wi th nand p InP , respect ively , and the potent ia l range for photoreduct ions on p I n P ex tended negat ive of the conduct ion bandedge. The e lec t rochemical behavior and magni tude of the unde r potent ia ls is compared to resul ts wi th InP in aqueous solutions and wi th o ther semiconductors in ACN. The semiconductor -so lu t ion interface poses in t e r est ing proper t ies which can be employed in the convers ion of l ight energy to e lect r ica l and chemical ene rgy by photoassis t ing e lec t ron t ransfe r be tween the semiconductor and solut ion species. InP is of pa r t i cu l a r in teres t because its bandgap of 1.25 eV is wel l sui ted for efficient use of solar energy in a photovoltalc threshold device (1). Al though InP tends to be uns table in aqueous solutions under i r radia t ion, p re vious studies by Wrighton et al. (2) have shown tha t n I n P can be used as a s table photoanode for the oxi dat ion of Te 2in aqueous solutions. These authors * E lec t rochemica l Society S tuden t Member . ** E lec t rochemica l Society Ac t ive Member .