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 CsPbI3, 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 CsPbI3−xBrx 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 CsPbI3−xBrx. 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.