Photoelectrochemical investigations on n-CdSe0.5Te0.5 thin-film electrode polyiodide system

Polycrystalline thin films of n-CdSe0.5Te0.5 have been prepared by vacuum flash evaporation of the n-CdSe0.5Te0.5 alloy. It is found that the films are n-type and show photoactivity in a 2 M KI+20 mM I-2 electrolyte. The films are characterized by X-ray diffraction and optical absorption studies. The optical absorption studies show the band-gap width to be approximate to 1.42 eV. Photoelectrochemical investigations have been carried out using the cell configuration n-CdSe0.5Te0.5 thin film/2 M KI + 20 mM I-2/C. Mott-Schottky plots are drawn using the space-charge capacitance data at 1 kHz frequency for various pH values of the electrolyte and are analysed to arrive at important and useful parameters. The frequency dispersion of the Mott-Schottky plots is also studied and the reasons for such behaviour are identified. The band diagram and the power output characteristics of the cell under AM 1 white-light illumination are discussed. Gartner's model is used to calculate the minority-carrier diffusion length and the donor concentration for as-grown and photoelectrochemically etched films. (C) 1998 Elsevier Science S.A. All rights reserved.