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Although organic–inorganic hybrid perovskite solar cells (PVSCs) have achieved dramatic improvement in device efficiency, their long‐term stability remains a major concern prior to commercialization. To address this issue, extensive research efforts are dedicated to exploiting all‐inorganic PVSCs by using cesium (Cs)‐based perovskite materials, such as α‐CsPbI₃. However, the black‐phase CsPbI₃(cubic α‐CsPbI₃and orthorhombic γ‐CsPbI₃phases) is not stable at room temperature, and it tends to convert to the nonperovskite δ‐CsPbI₃phase. Here, a simple yet effective approach is described to prepare stable black‐phase CsPbI₃by forming a heterostructure comprising 0D Cs₄PbI₆and γ‐CsPbI₃through tuning the stoichiometry of the precursors between CsI and PbI. Such heterostructure is manifested to enable the realization of a stable all‐inorganic PVSC with a high power conversion efficiency of 16.39%. This work provides a new perspective for developing high‐performance and stable all‐inorganic PVSCs.

Recently, the evolved intermediate phase based on iodoplumbate anions that mediates perovskite crystallization has been embodied as the Lewis acid–base adduct formed by metal halides (serve as Lewis acid) and polar aprotic solvents (serve as Lewis base). Based on this principle, it is proposed to constitute efficient Lewis acid–base adduct in the SnI₂deposition step to modulate its volume expansion and fast reaction with methylammonium iodide (MAI)/formamidinium iodide (FAI) (FAI is studied hereafter). Herein, trimethylamine (TMA) is employed as the additional Lewis base in the tin halide solution to form SnY₂–TMA complexes (Y = I⁻, F⁻) in the first‐step deposition, followed by intercalating with FAI to convert into FASnI. It is shown that TMA can facilitate homogeneous film formation of a SnI₂(+SnF₂) layer by effectively forming intermediate SnY₂–TMA complexes. Meanwhile, its relatively larger size and weaker affinity with SnI₂than FA+ ions will facilitate the intramolecular exchange with FA+ ions, thereby enabling the formation of dense and compact FASnI₃film with large crystalline domain (>1 µm). As a result, high power conversion efficiencies of 4.34% and 7.09% with decent stability are successfully accomplished in both conventional and inverted perovskite solar cells, respectively.

Organic–inorganic hybrid perovskite solar cells (PVSCs) have become the front‐running photovoltaic technology nowadays and are expected to profoundly impact society in the near future. However, their practical applications are currently hampered by the challenges of realizing high performance and long‐term stability simultaneously. Herein, the development of inverted PVSCs is reported based on low temperature solution‐processed CuCrO₂nanocrystals as a hole‐transporting layer (HTL), to replace the extensively studied NiO_xcounterpart due to its suitable electronic structure and charge carrier transporting properties. A ≈45 nm thick compact CuCrO₂layer is incorporated into an inverted planar configuration of indium tin oxides (ITO)/c‐CuCrO₂/perovskite/[6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM)/bathocuproine (BCP)/Ag, to result in the high steady‐state power conversion efficiency of 19.0% versus 17.1% for the typical low temperature solution‐processed NiO_x‐based devices. More importantly, the optimized CuCrO₂‐based device exhibits a much enhanced photostability than the reference device due to the greater UV light‐harvesting of the CuCrO₂layer, which can efficiently prevent the perovskite film from intense UV light exposure to avoid associated degradation. The results demonstrate the promising potential of CuCrO₂nanocrystals as an efficient HTL for realizing high‐performance and photostable inverted PVSCs.