High Efficiency of Cadmium Telluride Thin-Film Solar Cells Achieved Through Front and Back Surface Optimization

The global transition to renewable energy has made photovoltaics a potential primary energy source, due to the abundance of solar radiation worldwide and the technological maturity of conversion systems. In this context, cadmium telluride (CdTe) remains one of the leading thin-film absorber materials due to its near-optimal bandgap (~1.5 eV) and high absorption coefficient; however, conventional CdTe-based devices face three factors that limit their efficiency: parasitic absorption in the standard cadmium sulfide (CdS) window layer, non-radiative recombination at the interfaces, and the economically costly requirement for thick absorber layers (3 to 5 µm) given the high cost of CdTe. This work proposes a dual-interface passivation strategy that simultaneously addresses loss mechanisms at both the front and back surfaces. At the front interface, the conventional CdS buffer layer is replaced by a Cd(1−x)Zn(x)S alloy, whose tunable bandgap (2.4–3.7 eV) suppresses parasitic absorption in the ultraviolet and blue regions and improves band alignment with CdTe, thereby increasing the short-circuit current and open-circuit voltage. At the rear interface, a CuInTe2 (CIT) rear surface field layer is introduced between the CdTe absorber and the molybdenum (Mo) rear contact to counteract the Schottky barrier responsible for degrading hole collection. These two modifications, when implemented together, yield efficiency gains greater than those previously reported in the literature, while also enabling a substantial reduction in the thickness of the CdTe absorber to 1 µm. Using one-dimensional drift-diffusion simulations (wxAMPS) under standard AM 1.5G illumination, this study systematically evaluates the influence of the zinc content in the Cd(1−x)Zn(x)S buffer layer and the thickness of the CuInTe2 layer on the key photovoltaic performance metrics (Jsc, Voc, FF, and efficiency), with the aim of identifying the optimal device configuration for high-performance and cost-effective CdTe thin-film solar cells.