Surface‐Stabilized CsPbI3 Nanocrystals with Tailored Organic Polymer Ligand Binding

Perovskite nanocrystals (NCs) exhibit attractive photophysical properties by combining the excellent optoelectronic properties of bulk perovskites with the strong quantum confinement effect at the nanoscale. However, CsPbI3 NCs easily transform into a non-perovskite phase because of the ionic lattice and dynamic ligand binding. Herein, stable black-phase CsPbI3 NCs capped with a new organic ligand, HO-PS-N3 (HOPS), which consists of a polystyrene segment with hydroxyl and azide end groups, are reported. This organic polymer ligand passivated the surface defects and enhanced the stability of CsPbI3 NCs by exposing the linking hydrophobic polystyrene segment. Consequently, the optimized CsPbI3 NCs exhibit significantly improved resistance to moisture or light and maintained 70 % of the original luminous intensity after immersion in water for two months. The theoretical results revealed that the binding energy of the HOPS ligand on the surface of the CsPbI3 NCs is higher than that of the commonly used oleic acid, alleviating the defects-induced degradation during purification. Thus, surface-stabilized CsPbI3 NCs are beneficial for a broad range of optoelectronic applications.