The Stabilization of CsPbI3−xBrx Phase by Lowering Annealing Temperature for Efficient All‐Inorganic Perovskite Solar Cells

All‐inorganic perovskites are a promising solution for the fabrication of thermally stable perovskite solar cells (PSCs) with remarkable performances. However, a high annealing temperature is required for the stabilization of the photoactive phase of CsPbI 3 , which represents a limiting factor for their potential scaling‐up and manufacturing at industrial scale. This work demonstrates a new process for the stabilization of CsPbI 3− x Br x perovskite at lower annealing temperature of 180°, based on a rational halogen substitution enabled by the introduction of dimethylammonium (DMA) additives. Bromide inclusion favors indeed the conversion from the intermediate phases to CsPbI 3− x Br x . Standard mesoscopic solar cells prepared with this approach achieve a power conversion efficiency (PCE) of 14.86%, with reduced voltage losses and increased fill factor compared to the reference device. Moreover, this work proves that a rational substitution of the halide in the DMA salt is also beneficial for the devices annealed at higher temperature, achieving an encouraging PCE of 16.23%. By reducing the processing temperature, this new method widens the range of applications of all‐inorganic PSCs toward temperature‐sensitive materials and industrial applications.