Enhanced Amplified Spontaneous Emission from All‐Inorganic Perovskite Thin Films by Composition Engineering

Abstract All‐inorganic CsPbBr 3 perovskite thin films are regarded as promising gain media to realize electrically pumped green laser diodes due to their good stability. However, the amplified spontaneous emission (ASE) of CsPbBr 3 perovskite thin films suffers from a relatively high threshold due to their high defect density and large scattering loss. This work demonstrates high‐quality CsPbBr 3 /CsPb 2 Br 5 and CsPbBr 3 /Cs 4 PbBr 6 thin films using a vapor deposition method. Through rational design and modification on the compositions of thin films, it is found that the existence of CsPb 2 Br 5 or Cs 4 PbBr 6 phase in CsPbBr 3 can dramatically improve photoluminescence and lengthen carrier lifetime. The mixed phase films show good crystalline quality with lower trap density and enhanced spatial confinement. As a result, the ASE threshold of CsPbBr 3 perovskite thin film is reduced from 12.0 ± 0.2 to 10.1 ± 0.3 µJ cm −2 (with CsPb 2 Br 5 ) and 10.2 ± 0.2 µJ cm −2 (with Cs 4 PbBr 6 ). Furthermore, the optical gain is increased from 10.4 ± 0.5 to 21.6 ± 0.9 cm −1 (19.5 ± 0.8 cm −1 ) with the participation of CsPb 2 Br 5 (Cs 4 PbBr 6 ) phase. The findings provide an effective approach to lower the threshold of CsPbBr 3 lasers and shed light on the potential of stable electrically pumped perovskite lasers.