Postsynthesis Potassium-Modification Method to Improve Stability of CsPbBr3 Perovskite Nanocrystals

In this communication, a simple postmodification method to improve the optical properties and stability of CsPbBr3 perovskite nanocrystals (CPB-NCs) is reported. By strictly controlling the adding dose of K-oleate (molar ratio of K/Cs = 1.5/1) into the parent CPB-NC solution, it is possible to synthesize monodispersed K-modified CPB-NCs (K-CPB-NCs) with drastically enhanced photo- and thermostabilities as well as photoluminescence quantum yields, which are increased to 83% from 65%. Photostability tests show that the parent CPB-NC film drops to 50% of its original PL intensity after 45 h of illumination, but the K-CPB-NC film can maintain 100% of PL even after 153 h. Through the morphology, structure, and composition evolution of K-CPB-NCs, these benefits were attributed to the modification of K+ ions, which possibly induces a strong K-related protective passivation layer on the surface of K-CPB-NCs and simultaneously drastically decreases their surface defects.