Ultrastable CsPbBr Perovskite Quantum Dot and Their Enhanced Amplified Spontaneous Emission by Surface Ligand Modification.

The poor stability and aggregation problem of CsPbBr quantum dots (QDs) in air are great challenges for their future practical application. Herein, a simple and effective ligand-modification strategy is proposed by introducing 2-hexyldecanoic acid (DA) with two short branched chains to replace oleic acid (OA) with long chains during the synthesis process. These two short branched chains not only maintain their colloidal stability but also contribute to efficient radiative recombination. The calculations show that CsPbBr QDs with DA modification (CsPbBr -DA QDs) have larger binding energy than CsPbBr QDs with OA (CsPbBr -OA QDs), resulting in significantly enhanced stability. Due to the strong binding energy between DA ligands and QDs, CsPbBr -DA QDs exhibit no aggregation phenomenon even after stored in air for more than 70 d, and CsPbBr -DA QDs films can maintain 94.3% of initial PL intensity after 28 d, while in CsPbBr -OA QDs films occurs a rapid degradation of PL intensity. Besides, the enhanced amplified spontaneous emission (ASE) performance of CsPbBr -DA QDs films has been demonstrated under both one- and two-photon laser excitation. The ASE threshold of CsPbBr -DA QDs films is reduced by more than 50% and their ASE photostability is also improved, in comparison to CsPbBr -OA QDs films.