Preparation of CdTe thin film by electrodeposition in butyl methyl imidazolium bath at 80 °C

Abstract

CdTe thin films have been prepared on FTO substrates by eletrochemical deposition in a butyl methyl imidazolium chloride bath at 80°C potentiostatically at three different applied potentials. The electrodeposition process ensures the underpotential deposition of Cd on Te coated FTO substrate. CdTe thin film was grown at a relatively higher growth rate which resulted a typical thickness of 2.7μm for a deposition time of 1h at an applied deposition potential of −1.45V. The XRD pattern indicates the formation of cubic CdTe phase with zincblende structure. The Cd to Te ratio of the film can be nicely tuned in the range of 0.8–2.27 by the selection of deposition potential. The film deposited at a potential of perfect stoichiometry (−1.45V) shows interconnected clusters with an average size in the range of 40–100nm. The formation of CdTe cubic phase is also ascertained by the microdomain Raman analysis. Hot probe analysis indicates the P-type behavior of the CdTe film. The band gap energy of the CdTe film is found as 1.44eV from the UV–Vis measurements. A photoelectrochemical cell with the configuration: CdTe (0.5cm2) thin film |0.1M K2Sx(pH-9.2) |Pt (2cm2) has been constructed with the electrochemically deposited CdTe thin film. The photocurrent measurement under chopped light illumination shows an onset potential of 1V (w.r.t. satd. Calomel) for cathodic photocurrent. The onset potential for the cathodic photo current generation has been complemented by the flat band potential of 0.93V (w.r.t. satd. Calomel) from the Mott Schottky measurement in the same electrolyte.