Enhanced stability and brightness for small CsPbX3nanocrystalsvia solvent and ligand controlling

Abstract

CsPbX₃ (X = Cl, Br, I) nanocrystals (NCs) have attracted significant research interest for optoelectronic applications owing to their outstanding optical characteristics, including tunable band gaps, narrow luminescent peak and near-unity photoluminescence quantum yields (PLQYs). However, the practical application is limited by high synthesized temperature and inert atmosphere requirements during conventional hot-injection process. In this paper, the synthesis of CsPbX₃ (X = Cl, Br, and I) NCs in non-polar media was developed at room temperature using trimethylsilyl halides as halogen precursors and a ternary ligand system comprising dodecylbenzenesulfonic acid, oleic acid, and oleylamine. Namely, resulting CsPbBr₃ NCs display uniform dimensions averaging 5.5 nm. By precisely controlling Cs/Pb ratios, the phase compositions from zero-dimensional Cs₄PbX₆ NCs to three-dimensional CsPbX₃ NCs were adjusted. CsPbBr₃ NCs created using optimized conditions exhibited outstanding PL properties including high PLQYs (94.4 %), narrow full width at half maxima (15 nm) of PL spectra, and remarkable environmental stability (>90 days). Cs/Pb ratios play important role for tunable PL, in which CsPbBr₃ samples revealed bright blue to green emitting while the PL of CsPbI₃ NCs was adjusted from green, yellow to red. These results are ascribed to the interface controlling via ligand growth kinetics. In addition, the CsPbX₃ NCs synthesized by this method can maintain high stability under UV irradiation and water contact conditions, showing the application potential in the field of display. This work establishes a novel strategy for ambient-temperature synthesis of high-quality perovskite NCs with tunable PL performance.