Over 32% Efficient All-Inorganic Two-Terminal CsPbI2Br/Si Tandem Solar Cells: A Numerical Investigation

Cesium-based all-inorganic CsPbI2Br perovskite solar cells (PSCs) offer excellent thermal stability and an optimum bandgap for photovoltaic applications, making them promising alternatives to the thermally unstable organic-inorganic metal halide perovskites. State-of-the-art single-junction CsPbI2Br PSCs are yet to achieve high power conversion efficiency (PCE) of organic-inorganic hybrid counterparts. Herein, numerical simulations, through solar cell capacitance simulator-1D (SCAPS-1D), to demonstrate a highly efficient two-terminal tandem solar cell (TSC), with CsPbI2Br and a silicon heterojunction (a-Si:H/c-Si) as the top and bottom subcells, respectively, are used. The standalone subcells are first calibrated to match the experimental results reported in literature, followed by the evaluation of the tandem configuration. With 0.5 mu m-thick CsPbI2Br top cell, the bottom c-Si thickness is adjusted to match the top and bottom subcell currents, boosting the PCE to 26.25%. The PCE of the TSC can be further improved, by carefully selecting the electron and hole transport layers for the top PSC and by tuning the work function of the front-contact electrode. Under optimized and current-matched conditions, the proposed tandem design shows a conversion efficiency as high as 32.44%, enabling the pathway for highly efficient all-inorganic perovskite/silicon tandems.