Effect of varying cathodic voltages on the optical properties and electrical conductivity type of copper telluride thin films

The synthesis of copper telluride (CuTe) compound semiconductors has been carried out using the electrodeposition technique at a stable pH of 5.5 ± 0.2 and a bath temperature of 70 °C. Three thin films were deposited on fluorine-doped tin oxide (FTO) conducting glass substrates at cathodic voltages of 1500 mV, 1600 mV, and 1700 mV. The optical properties and electrical conductivity type of the thin films were characterised using relevant techniques such as UV/Vis spectroscopy and a photoelectrochemical (PEC) cell measurement instrument, respectively. All the deposited thin films possessed p-type electrical conductivity with varying magnitudes. The chronoamperometry results showed that the thickness of the CuTe layers increased with the increase in the cathodic voltage. The estimated film thicknesses were ~86, 140, and 146 nm for CuTe layers deposited at 1500 mV, 1600 mV, and 1700 mV, respectively. The result revealed the possibility of thinner layers having a very good absorption edge and better optical conductivity than thicker layers. The bandgap of the deposited thin films was found to be voltage-dependent, and the values vary between 2.50 and 3.00 eV ± 0.02. All the deposited CuTe layers exhibited low reflectance values, thus revealing the film’s importance in anti-reflectance coating. Since the electrodeposited CuTe layers exhibit p-type electrical conductivity within the explored voltage ranges, they can form a p-n heterojunction device with an appropriate n-type semiconductor.