Enhanced amplified spontaneous emission performance of inorganic perovskite by additive engineering

•Nonionic surfactant Polysorbate-20 (PS20) was adopted to control crystallization and growth of CsPbBrxI3-x perovskite.•PS20 modified CsPbBrxI3-x perovskite film exhibited smooth morphology and enhanced radiative recombination.•The modified perovskite behaved better ASE performance with a threshold of 4.72 μJ/cm2 and a gain factor of 1252 cm−1. All-inorganic perovskites have become promising optical gain medium due to excellent optical properties. For CsPbX3 thin films, optical losses caused by uneven morphology and non-radiative defects can hinder amplified spontaneous emission (ASE) performance. Here, we take advantage of additive engineering strategy to simultaneously control the morphology and defect states of CsPbBrxI3-x films via introducing Polysorbate-20 (PS20) into perovskite precursor. The optical gain coefficient of the CsPbBrxI3-x film increased from 491.1 cm−1 to 1252 cm−1 and ASE threshold decreased to 4.72 μJ/cm2. Moreover, the optimized perovskite film exhibited excellent linear polarization characteristics with high degree of polarization (DOP) of 88 %. Our research highlights the importance of defect passivation and morphology control to improve ASE performance.