Probing the significance of RF magnetron sputtering conditions on the physical properties of CdS thin films for ultra-thin CdTe photovoltaic applications

We comprehensively explored the impact of RF magnetron sputtering conditions on the physical properties of CdS thin films for the first time. Structural, morphological, and compositional properties were altered to a great extent by the sputtering conditions. Very high average transmittances of 94%, 92.5%, 91% and 89% were achieved in CdS thin films with thicknesses of 40, 60, 80, and 100 nm, respectively. A 100-nm thick CdS thin film showed an excessively high mobility of 92 cm²/V·s with an optimum carrier concentration of 10¹⁷ cm⁻³ and resistivity of 10³ Ω·cm. An ultra-thin CdTe film (480 nm) with a smooth and crack-free surface was achieved with RF magnetron sputtering. As proof of concept, ultra-thin CdTe solar cells were fabricated by incorporating CdS thin films with thicknesses varying from 40 to 100 nm, and the power conversion efficiency was enhanced from 1.18% to 4.13%, respectively. This work highlights the importance of investigating sputtering conditions to achieve CdS with superior physical properties and enhance ultra-thin CdTe solar cell performance.