2D Non‐Layered In2S3 as Multifunctional Additive for Inverted Organic‐Free Perovskite Solar Cells with Enhanced Performance

Organic‐free perovskite solar cells (PSCs) have been of rising interest due to their remarkable resistance toward long‐term thermal stress. Nevertheless, the inorganic perovskite films usually suffer from poor crystallization and high‐density defects in bulk and near/at the interfaces, which leads to significant charge recombination loss and hence inferior device performance. Herein, it is demonstrated that high‐quality CsPbI 2 Br perovskite films could be prepared by using 2D non‐layered materials as additives, such as In 2 S 3 nanoflakes (Nano‐In 2 S 3 ) with well‐matched lattices and unsaturated dangling bonds on the surface. In addition, it is found that the introduction of Nano‐In 2 S 3 results in not only defect passivation but also remarkable quasi‐Fermi level splitting across the perovskite film due to its gradient doping behavior, thereby enhancing the built‐in electric field in the inverted PSCs. As a result, the optimal devices based on Nano‐In 2 S 3 :CsPbI 2 Br absorber and all‐inorganic interfacial layers deliver a champion power conversion efficiency of 15.17% along with excellent ambient and thermal stabilities, superior to those of the pristine devices and comparable to the best organic‐free PSCs. A novel strategy for highly efficient and stable organic‐free photovoltaics by using 2D non‐layered materials as multifunctional additives is demonstrated.