Interface of n-type WSe2 photoanodes in aqueous solution. I. Electrical properties.

Abstract

Transport properties of n-type ${\mathrm{WSe}}_{2}$ single crystals and dark electrical properties of a polyiodide aqueous electrolyte/n-type ${\mathrm{WSe}}_{2}$ interface are reported in this paper. The conductivity anisotropy (${\mathrm{\ensuremath{\sigma}}}_{\mathrm{\ensuremath{\parallel}}}$/${\mathrm{\ensuremath{\sigma}}}_{\mathrm{\ensuremath{\perp}}}$) has been measured versus the temperature, it is found practically temperature independent but sample dependent; suggestions are made about the conduction across the layers. Electrical properties of the electrolyte/semiconductor interface were investigated by various methods such as I-V, C-V, G-V, and admittance spectroscopy. Perpendicular electrodes with various surface conditions and electrodes parallel to the c axis were studied in order to better understand the role played by surface defects such as steps. It is shown, for example, that much caution has to be taken in interpreting C-V measurements of stepped electrodes. Our results indicate that the conductivity anisotropy greatly enhances the electronic transfers occurring through the steps.