High Optical Gain of Solution‐Processed Mixed‐Cation CsPbBr 3 Thin Films towards Enhanced Amplified Spontaneous Emission

• Published in: Advanced functional materials 2021-06, Vol.31 (25)
• Main Authors: Li, Meili, Shang, Qiuyu, Li, Chun, Li, Shuai, Liang, Yin, Yu, Wenjin, Wu, Cuncun, Zhao, Liyun, Zhong, Yangguang, Du, Wenna, Wu, Xianxin, Jia, Zhili, Gao, Yan, Chen, Hui, Liu, Xinfeng, Guo, Shaojun, Liao, Qing, Xing, Guichuan, Xiao, Lixin, Zhang, Qing
• Format: Article
• Language: English
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202102210

A solution‐processed thin film made of all‐inorganic CsPbBr 3 perovskite is a promising candidate for low‐cost and flexible green‐color lasers. However, the amplified spontaneous emission (ASE) of solution‐processed CsPbBr 3 films still experiences a high threshold owing to poor morphology and insufficient optical gain. Here, a multiple‐cation doping strategy is demonstrated to develop compact, smooth thin films of Cs 0.87 (FAMA) 0.13 PbBr 3 /(NMA) 2 PbBr 4 (FA: formamidinium; MA: methylammonium; NMA: naphthylmethylammonium) with a record high net modal optical gain of ≈ 3030 cm −1 and low propagation loss of 1.0 cm −1 . The FA and MA cations improve the crystallization kinetics to form continuous films, and the NMA cations reduce the grain dimension, increase film dispersibility/uniformity, and enhance spatial confinement to promote optical gain. Room‐temperature ASE is demonstrated under a low threshold of ≈ 3.8  µ J cm −2 without degradation after four months of storage in glove box or excitation by 3 × 10 7 laser pulses. These findings provide insights into enhancing the optical gain and lowering the threshold of perovskite lasers in terms of molecular synthesis and microstructure engineering.