The sensitized p-type photoelectrode for dye sensitized photoelectrochemical solar and water splitting cells is a major limitation in the development of tandem dye sensitized cells. Recently, we have found that Zn substituted Co3O4 spinel as a hole transport layer in dye sensitized p-type solar cell results to an increase in internal quantum efficiency compared to NiO. In this study, we observe the surface of Zn/Ni substituted Co3O4, Co3O4, and NiO through photoemission spectroscopy and compare the species present on the surface with those in the bulk as analyzed through x-ray diffraction and energy dispersive x-rays. Although the metal spectra remain almost the same in various samples, the oxygen spectra (O 1S) vary and this indicates a significant role of surface oxygen in the reactivity. The workfunction was measured as a function of atomic concentration of Zn/Ni and was found to be in the range of 4.5-4.8 vs vacuum, and has direct correlation with atomic fraction Zn but not with Ni. This interesting difference in the behavior with Zn and Ni substitution and the role of surface species are proposed to be the main contributors to the improvement observed in quantum efficiency.

Surface and bulk characteristics of Zn/Ni substituted cobalt oxide spinel p-type semiconductors

249th National Meeting (2015)

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