Bromide complimented methylammonium-free wide bandgap perovskite solar modules with high efficiency and stability

Wide bandgap metal-halide perovskites are promising photoactive materials to pair with silicon in tandem solar cells to achieve power conversion efficiency (PCE) higher than 30% at low cost. In this work, we found that massive defects are generated in wide bandgap perovskites due to the release of bromide under mild annealing (100 °C), which restrains the open-circuit voltage and thus the performance of solar cells. We report a bromide complementation strategy for wide bandgap perovskites via surface treatment with trimethylphenylammonium bromide (PTABr). As a result, significantly reduced charge recombination and elongated carrier lifetime are achieved, which improves both efficiency and stability of solar cells. A champion PCE of 17.0% for large-area (5 cm × 5 cm) modules with an active area of 10 cm2 is achieved, which is one of the best performance of perovskite solar modules based on wide bandgap perovskites. The solar cells and modules show enhanced stability under the stress of moisture, illumination and heat. Moreover, we achieve a PCE of 25.0% with four-terminal perovskite/silicon tandem solar cells. These results suggest that bromide complementation is a promising way in obtaining high efficiency and large-area perovskite/Si tandem solar cells with good stability.