Ultrasmall CsPbBr3 Quantum Dots with Bright and Wide Blue Emissions

Abstract

Low‐dimensional metal halide perovskites have been widely regarded due to their unique crystal structure and photophysical properties. Herein, blue‐emission CsPbBr3 quantum dots (QDs) or nanocrystals (NCs) with extremely small crystal size (1–2 nm) but high photoluminescence quantum yield (PLQY, 72.4%) are synthesized with a new surface ligand, single (6‐amino‐6‐deoxy) beta cyclodextrin (6A‐βCD), which also acts as the confined‐growth template for such small QDs. Detailed photoluminescence spectrum and femtosecond transient absorption spectrum study proves that the blue emission with multiple peaks originates from both band‐edge radiation and exciton recombination. Furthermore, as a result of the small size, exciton localization in the form of self‐trapped excitons (STEs) and significant quantum size confinement effect are both important reasons for the efficient and wide blue emissions of these QDs. This work provides a new strategy not only to synthesize ultrasmall perovskite QDs but also to develop blue perovskite‐QD light‐emitting devices.