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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 CsPbI2Br perovskite films could be prepared by using 2D non‐layered materials as additives, such as In2S3 nanoflakes (Nano‐In2S3) with well‐matched lattices and unsaturated dangling bonds on the surface. In addition, it is found that the introduction of Nano‐In2S3 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‐In2S3:CsPbI2Br 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. [ABSTRACT FROM AUTHOR]

Cesium‐based all‐inorganic perovskites (PVKs) are prized for their high thermal stability and wide bandgap suitable for the top layer of tandem solar cells. To further boost the photovoltaic performance of inorganic PVK solar cells (PeSCs), a variety of strategies aiming to either passivate defects or enhance the electric field are developed. Nevertheless, a double‐aim strategy is less explored. Herein, a facile strategy of gradient doping is adopted for optimizing the inverted CsPbI2Br PeSCs. Particularly, a bicationic iodine salt, namely 2,2′‐bis(trifluoromethyl)‐[1,1′‐biphenyl]‐4,4′‐diamine iodine (BFBAI2), is used to realize gradient doping in PVK and ZnO layers, respectively. As a result, the inverted PeSCs with the doped PVK/ZnO bilayer deliver improves power conversion efficiency (PCE) up to 14.38% along with enhanced device stability under ambient or thermal aging conditions, greatly surpassing the pristine devices. The improvements are attributed principally to the low‐defect PVK layer as well as enhanced electric field across the inverted PeSCs upon gradient doping. This work thus demonstrates an efficient bifunctional strategy toward highly efficient and stable CsPbI2Br PeSCs with inverted configuration. [ABSTRACT FROM AUTHOR]

[Display omitted] • A double-side healing strategy is applied to modify the CsPbI 2 Br/ZnO interface. • The conduction through perovskite grain is greatly improved via this strategy. • The built-in electric field across the perovskite film is remarkably enhanced. • A better electric contact at the CsPbI 2 Br/ZnO interface is achieved. • The inverted devices deliver a PCE of 15.36% and excellent operational stability. Inorganic perovskite solar cells (PSCs) with inverted (p-i-n) configuration are important for the development of tandem solar cells. Nevertheless, inverted all-inorganic PSCs still remain challenging due to the high-density defects in the perovskite and inorganic charge-transporting layer. Herein, we demonstrate a double-side healing strategy to simultaneously improve the performance of perovskite and electron transporting layer (ETL). Specifically, bipyrimidine hydroiodide (BP-HI) is introduced at the CsPbI 2 Br/ZnO interface in inverted PSC. A combined microscopic, mass spectrometric and spectroscopic study reveals that the BP-HI could diffuse into not only perovskite grain boundaries (GBs) but also the ZnO layer. This double-side healing leads to improved conduction through perovskite grain, suppressed ion-migration along perovskite GBs, enhanced built-in electric field cross perovskite film and better electric contact at the PVK/ZnO interface. As a result, the optimized PSCs deliver a champion PCE of 15.36% along with a stabilized power output (SPO) of 15.05%. Meanwhile, these PSCs also display excellent long-term operational stability under ambient conditions. This work thus provides a feasible route for improving the performance and stability of inverted PSCs. [ABSTRACT FROM AUTHOR]