Photoelectrochemical study of electrochemically synthesized CdTe thin films from acetate-anion based ionic liquid bath

Potentiostatic deposition of CdTe thin films from acetate-anion based ionic liquid, 1-butyl-3-methylimidazolium acetate ([BMIM][Ac]) bath has been carried out at 90 °C. A molar concentration ratio i.e. molar Cd/Te = 2 has been taken to electrochemically synthesize CdTe films under different dynamic conditions. FE-SEM showed the formation of homogeneous CdTe films over fluorine doped tin oxide (FTO) substrates. EDX revealed the formation of nearly stoichiometric CdTe films at optimal stirring rate of ∼400 rpm. The optical band gap of ∼1.45eV were observed with cubic zinc blende CdTe structure. XRD, RAMAN and XPS analysis confirmed the formation of pure CdTe phase with ultra-thin oxide over-layer. Photoelectrochemical studies of CdTe photoelectrodes prepared by electrodeposition technique was investigated in K2Sx and KH2PO4. Mott-Schottky analysis demonstrated the formation of p-CdTe with a flatband (Vfb) potential of ∼0.95VRHE. A high photocurrent density of 1.23 mA/cm2 has been achieved with solar conversion efficiency (ηc) of 1.50% for the pristine electrodeposited CdTe/FTO photocathode i.e. without surface modification, under chopped monochromatic illumination. This illustrates that the prepared CdTe photocathode can be a promising semiconductor candidate for application in photoelectrochemical hydrogen evolution from water. The use of acetate-anion based IL bath always resulted in p-type CdTe thin films.