Year-Long Stability and Near-Unity Photoluminescence Quantum Yield of CsPbBr₃ Perovskite Nanocrystals by Benzoic Acid Post-treatment

Abstract

The challenges afflicting cesium lead halide perovskite nanocrystals (PNCs) are long-term stability and deterioration of photoluminescence (PL) properties with time, hindering its commercialization applicability. The presence of surface defects on cesium lead bromide (CsPbBr3) PNCs commonly lead to the degradation of PL properties via ligand loss. In this work, we explored benzoic acid post-treatment to improve the PL and long-term stability of green-emitting CsPbBr3 PNCs. The surface defects are passivated via co-ordination of carboxyl group with under coordinated surface lead atoms. The photoluminescence quantum yield is in unity with benzoic acid (BA) post-treatment, also reflected in PL decay profiles. The BA-CsPbBr3 PNCs exhibit excellent stability for more than a year. Thirty-six percent of the initial PL intensity is preserved for BA-CsPbBr3 PNCs, while the PL is completely quenched for untreated CsPbBr3 PNCs within 24 h of continuous UV illumination (λex = 365 nm). Nearly 21% of the PL is preserved for BA-CsPbBr3 PNCs, whereas the PL is quenched instantly for untreated PNCs with ethanol treatment. The green emission from the fabricated down-conversion LED device plotted in CIE 1931 demonstrated high color purity.