All inorganic cesium lead halide perovskite (CsPbX 3 ; X = Cl, Br, or I) quantum dots (QDs) have received widespread attention as a class of favorable optical gain materials. The key issue of CsPbX 3 perovskites is their instability under light or exposure to air. Notably, the inherent phase instability of CsPbI 3 QDs severely restricts the development of red-light emission. Herein, we propose a simple method to post-process CsPbBr 3 QDs with a ZnI 2 solution. The prepared CsPbBr y I 3−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 Zn 2+ . Compared with the pristine CsPbBr 3 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. 

ZnI<sub>2</sub> post-processing of CsPbBr<sub>3</sub> quantum dots for red, stable, and low-threshold amplified spontaneous emission

Organic additives can enhance the amplified spontaneous emission (ASE) performance of inorganic cesium lead halide perovskites (CsPbBr3 ) but volatility, potential hygroscopicity and oxidative degradation of these additives jeopardizes the thermal stability and shelf-life of blended CsPbBr3 films. To address this problem, we have fabricated perovskite films in a two-step solution protocol involving as little added polyethylene oxide (PEO) as possible. These films exhibited enhanced crystallization, improved photoluminescence (PL) intensity and prolonged lifetimes. Their hierarchical morphology and surface passivation lowered the ASE threshold from 278 to 176 μЈ/cm2 under one-photon nanosecond laser excitation. The proportion of added PEO was 0.3 wt% and was subsequently almost fully removed, thereby reducing its adverse influence on the stability of resulting films under continuous pulsed laser excitation. Stable ASE spectra could be stimulated after storage in air for 10 months.

Kun Tian

Papers

Low-Threshold Amplified Spontaneous Emission from Air-Stable CsPbBr3 Perovskite Films Containing Trace Amounts of Polyethylene Oxide.