Efficient and Stable Graded CsPbI3−xBrx Perovskite Solar Cells and Submodules by Orthogonal Processable Spray Coating

Inorganic perovskite solar cells (PSCs) are promising for achieving long-term operational stability with good device performance. Here, we report the fabrication of inorganic CsPbI2Br-based perovskite thin films with a well-defined CsPbI3−xBrx composition gradient in the surface region by a scalable, orthogonal processable spray-coating approach. The graded structure broadens absorption wavelength range and increases carrier lifetime, but it also causes electrical field redistribution within a device stack for more efficient charge separation and collection. With this approach, we obtained a power conversion efficiency of 16.81% for a 0.096-cm2 PSC. We further demonstrated a monolithically integrated perovskite submodule based on the graded CsPbI3−xBrx by spray coating with an efficiency of 13.82% (112-cm2 aperture area) and ∼9% degradation over 1,000-h continuous 1-sun light soaking.