Influence of a Copper Layer on the Functional Behaviour of a Cadmium Telluride Solar Cell Processed via Thermal Evaporation

Cadmium telluride (CdTe) has emerged as a popular option for the solar cell industry because of its favourable optical and electrical properties. The addition of a copper (Cu) layer presents a potential opportunity to enhance the performance of CdTe solar cells, thereby affecting the device functionality. This study investigated the influence of the deposition temperature for the Cu layer on the performance of CdTe solar cells. Using the thermal evaporation method, a 100-nm-thick Cu layer was deposited and subsequently annealed at temperatures of 200°C, 300°C, 400°C, and 500°C. The study evaluated various performance metrics including electrical conductivity, transmittance, current–voltage characteristics, Tauc spectra, and quantum efficiency. X-ray diffraction (XRD) was employed as a comprehensive characterization technique to analyse the morphological and structural changes induced by the Cu layer. The results indicate that higher deposition temperatures improve the electrical conductivity of CdTe solar cells, with optimal conductivity observed at 400°C due to enhanced crystallinity and reduced structural defects. Through copper doping and varying the deposition temperature, maximum efficiency of 87% and optical transmittance of up to 78% were achieved, along with open-circuit voltage (V_OC) of 0.86 V and short-circuit current density (J_SC) of 27.8 mA/cm² at a deposition temperature of 400°C.