Amplified Spontaneous Emission with a Low Threshold from Quasi‐2D Perovskite Films via Phase Engineering and Surface Passivation

Solution-processed quasi-2D Ruddlesden-Popper perovskites are being considered as a promising optical gain medium in lasing applications, owing to their outstanding optoelectronic properties and inherent stability. However, the development of quasi-2D perovskites for lasers with low threshold and high optical gain is still lagging far behind 3D-perovskites. This work proposes an anti-solvent treatment strategy to regulate the phase components and surface morphology of quasi-2D PEA2(CsPbBr3)n−1PbBr4 thin films. Furthermore, an additional poly(methyl methacrylate) coating is introduced to reduce the surface defects of perovskite films and suppress the non-radiative recombination. Due to the phase engineering and surface passivation, excellent amplified spontaneous emission (ASE) is obtained with a low threshold of 11.7 µJ cm−2 and a high net model gain of 622 cm−1. In addition, under 800 nm femtosecond laser excitation, two-photon-pumped ASE is also successfully observed with a low threshold of 7.2 mJ cm−2.