Revealing trace water effect on the structural and optical evolutions of blue CsPbBr3 perovskite quantum dots

Quantum confined blue CsPbBr3 perovskite quantum dots (PeQDs) demonstrate superior spectral stability and easy tunability by particle size relative to their mixed halide counterparts. However, their practical application is hampered by their susceptibility to moisture-induced degradation. Herein, the structural and optical evolutions of blue CsPbBr3 PeQDs induced by trace water are systematically studied and their mechanism is elucidated. Experimental results show that trace water (H2O) induces red shift of spectra from blue to green, accompanying significant increase in photoluminescent quantum yield and one order lower non-radiative recombination rate. Furthermore, the H2O-treated PeQDs' size presents obvious increase from 6.3 to 8.0 nm without obvious change in crystalline pattern. By combining experimental characterizations, first-principles calculations, and verification experiments, we demonstrate that appropriate H2O exposure is responsible for substituting oleic acid ligand on PeQDs, resulting in particle growth and spectral red shift. Our work establishes that water attacks PeQDs via acid–base chemistry at surface ligand sites—a mechanistic insight critical for enhancing moisture stability in blue CsPbBr3 PeQDs.