Amine- and Acid-Free Synthesis of Stable CsPbBr₃ Perovskite Nanocrystals

Ligands binding to all-inorganic lead halide perovskite nanocrystals (IPNCs) are easy to detach from the surface through proton exchange, causing severe stability issues in practical applications. Here, we have reported an amine- and acid-free approach for the synthesis of CsPbBr₃ IPNC with highly improved photochemical stability. The reaction mechanism follows a trioctylphosphine-mediated surface passivation route, which provides a proton-free reaction environment to stabilize the ligand capping on the surface of IPNCs. Nuclear magnetic resonance, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy characterizations reveal that the IPNCs possess a lead-rich surface passivated by carboxylates. The surface capping motif endows IPNCs with comprehensively improved stability against air, water, light, and heat. The IPNCs withstand exposure to ethanol in room light for 30 days and show nearly no fluorescent quenching. More importantly, the IPNCs present high resistance to intense light irradiation. Under continuous irradiation by 10 W/cm² blue light in open air, the lifetime of the IPNCs reaches over 2000 h, catching up the photostability of CdSe QDs. The white LEDs based on the IPNCs display a wide color gamut of 122% NTSC and luminous efficacy of 71 lm/W.