Ethylenediammonium Dihalide Assisted Direct Synthesis of Highly Luminescent and Stable CsPbX₃ (X = Cl, Br, I) Perovskite Nanocrystals

Abstract Colloidal cesium lead halide (CsPbX 3 , X = Cl, Br, I) perovskite nanocrystals (NCs) hold promises in photovoltaic and optoelectronic applications. However, their poor long‐term stability results in degradation of optical properties under ambient conditions. Various methods have been explored to address these issues. In this study, we demonstrate that following 3‐precursor hot‐injection method employing ethylenediammonium dihalide (EDAX 2 ) as an additional ligand/halide source one can obtain phase‐pure, monodispersed, stable, and highly luminescent CsPbX 3 NCs. Our violet‐emitting CsPbCl 3 , blue‐emitting CsPbClBr 2 , Green‐emitting CsPbBr 3 , yellow‐emitting CsPbBr 2 I, and red‐emitting CsPbI 3 NCs show PLQYs of 53%, 97%, 96%, 93%, and 95%, respectively. Moreover, the CsPbI 3 NCs, which are known for their phase instability, exhibit stability for up to two months under ambient conditions. The enhanced stability and photoluminescence are attributed to strong binding of the bidentate ligand (EDA 2+ ) to the surface of the NCs and effective removal of the halide‐deficiency trap states by X − .