Long-term air-stable amplified spontaneous emission in quasi-2D perovskite films through ligand engineering†

Lead halide perovskite films show great potential as laser gain media owing to excellent optoelectronic properties but suffer from their inherent instability. Quasi-two-dimensional (2D) perovskite with long-chain ligands has been considered as a promising candidate for robust lasing operating in air. However, quasi-2D perovskites with different long-chain amine ligands exhibit various properties and the underlying mechanism still remains unclear, making it difficult to find suitable long-chain amine ligands for perovskite films with both air-stability and excellent lasing performance. Herein, long-term air stable amplified spontaneous emission with a very low threshold is demonstrated in octylammonium (OA)-CsPbBr₃ films. The air stability of quasi-2D CsPbBr₃ films with several common long-chain ligands is compared and the superior stability of the OA-CsPbBr₃ film among these perovskite films is attributed to intrinsically hydrophobic organic ligands distributed on the film surface owing to preferred orientation. Furthermore, the OA-CsPbBr₃ film without any encapsulation exhibits consistent low-threshold amplified spontaneous emission during long-term storage over 8 months in air, suggesting the tremendous potential of OA-CsPbBr₃ film as a robust laser medium for long-term operation in air.