Inorganic lead halide perovskite materials (e.g., CsPbI 3 ) have a great potential to be used in light-emitting diodes (LEDs). However, poor stability of CsPbI 3 has limited its application. In this work, CsPbI 3 nanocrystals (NCs) show excellent stability (up to 60 days) under ambient and heating conditions (100 °C). Moreover, the performance of the tetra-n-butylammonium iodide (TBAI)-assisted CsPbI 3 NCs obtained under different reaction times is also investigated and compared, suggesting that 15 s is the optimum reaction time for NC synthesis. Furthermore, a mechanism of stability enhancement is also proposed, indicating TBAI is very critical to retard phase transition from cubic to orthorhombic structures. This study provides important insights into the synthesis of perovskite CsPbI 3 NCs with high stability toward LED applications.

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Perovskite solar cells (PSCs) have attracted significant research efforts due to their remarkable performance. However, most perovskite films are prepared by the antisolvent method which is not suitable for practical applications. Herein, a (FA0.83MA0.17)0.95Cs0.05Pb(I0.83Br0.17)3 (CsFAMA) perovskite film fabrication technique is developed using solvent volatilization without any antisolvents. The films are formed through recrystallization via the intermediate phase CsMAFAPbI x Cl y Br z during annealing, leading to high‐quality perovskite films. The perovskite growth mechanism is investigated in terms of controlling the amount of formamidinium iodide and methylammonium chloride in the precursor solutions. The oriental growth of the films via the intermediate phase is confirmed by the grazing‐incidence wide‐angle X‐ray scattering measurements. The photovoltaic properties of the perovskite films are investigated. The PSCs based on the films fabricated using the method exhibit a high efficiency of 20.6%. The method developed in this work is based on solvent volatilization, which exhibits significant potential in high reproducibility, facile operation, and large‐scale production.