Electrodeposition of CdTe Thin Film from Acetate-Based Ionic Liquid Bath

摘要

CdTe being a direct band gap semiconductor, is mostly used in photovoltaics. Here we present the synthesis of CdTe thin film on fluorine doped tin oxide (FTO) substrate potentiostatically using l-butyl-3-methylimidazolium acetate ([Bmim][Ac]) ionic liquid (IL) bath at 90 °C. Major advantages of using electrodeposition involves process simplicity, large scalability & economic viability. Some of the benefits offered by IL electrolytic bath are low vapour pressure, wide electrochemical window, and good ionic mobility. Cd(CH_3COO)_2 (anhydrous) and TeO_2 were used as the source precursors. The IL electrolytic bath temperature was kept at 90 °C for deposition, owing to the limited solubility of TeO_2 in [Bmim][Ac] IL at room temperature. Cathodic electrodeposition was carried out using a three electrode cell setup at a constant potential of-1.20 V vs. platinum (Pt) wire. The CdTe/FTO thin film were annealed in argon (Ar) atmosphere. Optical study of nano structured CdTe film were done using UV-Vis-IR and Raman spectroscopy. Raman analysis confirms the formation of CdTe having surface optics (SO) mode at 160.6 cm~(-1) and transverse optics (TO) mode at 140.5 cm~(-1). Elemental Te peaks at 123, 140.5 and 268 cm~(-1) were also observed. The optical band gap of Ar annealed CdTe thin film were found to be 1.47 eV (absorbance band edge~ 846 nm). The optimization of deposition parameters using acetatebased IL electrolytic bath to get nearly stoichiometric CdTe thin film is currently being explored.