Characterization of Sb2Te3 thin films prepared by electrochemical technique

Abstract

A conductive and thermally stable material with a high work function is required to produce highly efficient CdTe-based thin film solar cell (TFSC) devices. In this study, we report the growth of layers of polycrystalline, stoichiometric, and compact antimony telluride (Sb2Te3) by using the wet-chemical aqueous electrochemical technique. A three-electrode geometry consisting of a working electrode, a reference electrode, and a counter electrode was used to deposit the Sb2Te3 thin films at a low temperature (60 °C ± 2 °C). The growth potential was optimized through cyclic voltammetric measurements with reference to the Ag/AgCl reference electrode. The structural, morphological, compositional, and electrical properties of the films were studied and correlated. Their prominent Bragg reflections of (103), (016), and (110) verified the growth of the rhombohedral crystal structure of Sb2Te3. The Raman modes Eg and A1g, observed at 119.88 and 161.48 cm−1, respectively, confirmed the formation of the Sb2Te3 compound. Compact grain growth with a void-free and well-adherent layer was observed using scanning electron microscopy. The grain size, surface morphology, and thickness of the Sb2Te3 layers were significantly influenced by variations in the deposition potentials. An EDS analysis of the sample grown at −0.5 V revealed nearly stoichiometric growth (2:3, Sb:Te ratio). The elemental chemical states were studied through XPS analysis. The survey scan confirmed the presence of antimony, tellurium, oxygen, and carbon. The current–voltage characteristics reflected the nearly ohmic nature of the Sb2Te3 thin films. The ideality factor and carrier concentration obtained for the sample grown at −0.5 V exhibited nearly ohmic behaviors, with a high conductivity that was suitable for back-contact between the buffer layer and CdTe for the development of CdS/CdTe solar cells.