Air‐Processed MAPbBr3 Perovskite Thin Film with Ultrastability and Enhanced Amplified Spontaneous Emission

The poor stability, in particular with respect to temperature, moisture, and light exposure, remains a ubiquitous impediment virtually for metal halide perovskite materials and devices in their future practical application. Herein, from the perspective of precursor solution chemistry, ionic liquid solvent methylammonium acetate (MAAc) is introduced to prepare high‐quality MAPbBr3 perovskite thin films in a one‐step air‐processing process without anti‐solvent treatment. Due to formation of pinhole‐free, uniform, and compact MAPbBr3 perovskite film, excellent amplified spontaneous emission (ASE) with high emission efficiency and low threshold is obtained under nanosecond laser. Furthermore, the prepared MAPbBr3 perovskite exhibits excellent two‐photon induced ASE with a low threshold of 100 µJ cm−2 under 800 nm femtosecond laser excitation. More importantly, in comparison with the traditional MAPbBr3 films prepared with N,N‐dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), the MAPbBr3 film prepared with MAAc shows excellent optical stability: no signs of degradation under more than 2 h pulsed laser excitation, stable ASE emission spectra under the humidity of 95% and ASE spectra can be stimulated when films are kept in air for more than 6000 h without encapsulation. Herein, a novel ionic liquid solvent methylammonium acetate (MAAc) is introduced to prepare high‐quality MAPbBr3 perovskite films through one‐step air‐processing without antisolvent treatment. These films with excellent optical and moisture stability exhibit high efficiency and low threshold amplified spontaneous emission (ASE) under the irradiation of a nanosecond laser, which show great potential for stable perovskite lasers.