ZnI2 post-processing of CsPbBr3 quantum dots for red, stable, and low-threshold amplified spontaneous emission

All inorganic cesium lead halide perovskite (CsPbX3; X = Cl, Br, or I) quantum dots (QDs) have received widespread attention as a class of favorable optical gain materials. The key issue of CsPbX3 perovskites is their instability under light or exposure to air. Notably, the inherent phase instability of CsPbI3 QDs severely restricts the development of red-light emission. Herein, we propose a simple method to post-process CsPbBr3 QDs with a ZnI2 solution. The prepared CsPbBryI3−y (named CPBI-z, where z corresponds to the photoluminescence peaks' position) QDs exhibit adjustable photoluminescence in the range of 550–640 nm. The photoluminescence quantum yield is increased from 73.3% to 97.2% as the surface defects of QDs are passivated by I− and Zn2+. Compared with the pristine CsPbBr3 QDs, the post-processed QDs are more stable under ultraviolet irradiation and in the air. Aside from that, under 532 nm nanosecond laser excitation, CPBI-z QD films exhibit excellent amplified spontaneous emission performance. The CPBI-640 QD film shows a low threshold, 102 μJ cm−2 for red stable amplified spontaneous emission.