Preparation and optimization of all-inorganic CdSe/ZnTe solar cells

Cadmium selenide (CdSe) demonstrates high potential as a top cell material for Si-based tandem applications. However, obtaining high-quality CdSe thin films presents a significant challenge. Additionally, the intrinsic n-type conduction of CdSe desires a well-matched wide bandgap p-type partner to form a p-n junction for efficient photovoltaic applications. Herein, the vapor transport deposition method is employed to fabricate CdSe thin films with large grain sizes (∼2 μm), high crystallinity (with (002) preferred orientation), and strong band-edge photoluminescence. Moreover, zinc telluride (ZnTe), a II-VI group compound showing a low lattice mismatch of <0.7 % with CdSe, is explored as a p-type layer to construct solar cells. The properties of ZnTe thin film have been extensively studied and analyzed. By studying the annealing temperature (300 °C–550 °C), we obtained ZnTe film with a wide bandgap of 2.17 eV and conductivity of 1.4 × 10−5 S cm−1. To further enhance the carrier density of the ZnTe film, we employ a Cu doping strategy involving treatment with varying concentrations of CuBr solution (0 mg mL−1, 1 mg mL−1, 2.5 mg mL−1, 10 mg mL−1). Ultimately, a power conversion efficiency (PCE) of 2.03 % is achieved in CdSe/ZnTe solar cells. This is a primary exploration of all-inorganic CdSe/ZnTe solar cells, proving their potential for photovoltaic applications. Further optimization is deserved to achieve higher PCE.