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The practical applications of perovskite solar cells (PSCs) are limited by further improvement of their stability and performance. Additive engineering and interface engineering are promising medicine to cure this stubborn disease. Herein, an alkali metal fluoride as an additive is introduced into the tin oxide (SnO2) electron transport layer (ETL). The formation of coordination bonds of F– ions with the oxygen vacancy of Sn4+ ions decreases the trap-state density and improves the electron mobility; the hydrogen bond interaction between the F ion and amine group (FA+) of perovskite inhibits the diffusion of organic cations and promotes perovskite (PVK) stability. Meanwhile, the alkali metal ions (K+, Rb+, and Cs+) permeated into PVK fill the organic cation vacancies and ameliorate the crystal quality of PVK films. Consequently, a SnO2-based planar PSC exhibits a power conversion efficiency (PCE) of 20.24%, while the PSC modified by CsF achieves a PCE of 22.51%, accompanied by effective enhancement of stability and negligible hysteresis. The research results provide a typical example for low-cost and multifunctional additives in high-performance PSCs.

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Inorganic cesium lead halide perovskite solar cells have attracted widespread attention owing to their excellent stability relative to organic–inorganic solar cells. However, all‐inorganic perovskite solar cells without hole transport layers and using carbon layers as electrodes have serious energy level mismatch problems. To overcome this problem, here, the CsPbIBr2 surface is treated with 4‐aminomethyltetrahydropyran acetate to form a gradient energy band on the CsPbIBr2 perovskite/carbon interface. As a result, the hole extraction efficiency is successfully improved, and the morphology and crystallization of the perovskite layer are also improved. Moreover, the nonradiative recombination inside the perovskite and the charge recombination at the interface are effectively inhibited. Therefore, the power conversion efficiency of CsPbIBr2 solar cell is enhanced to 10.12%, and the high photovoltage of 1.32 V is obtained under one solar illumination, which are both higher than the pristine one (7.79%, 1.23V, respectively).