Red Low-threshold Amplified Spontaneous Emission of Perovskite Films Achieved by A-site Substitution and Defect Passivation
Lead halide perovskite has shown great potential as a new generation of optoelectronic materials due to its adjustable optical band gap,high luminous color purity,high carrier mobility,and solution-processibility.Cur-rently,amplified spontaneous emission(ASE)and laser have been realized in the blue,green,red,and even infra-red ranges for perovskite material.As a red light-emitting optical gain medium,CsPbI2Br perovskite material has good thermal stability and a suitable optical band gap and has attracted extensive attention from researchers.Howev-er,CsPbI2Br films prepared by the solution method are prone to phase transition in high-humidity environments,and there are many defects in the films,which hinder their further development.To improve the phase stability of CsPbI2Br perovskite films,the A-site is partially substituted by FA+(CH4N2+)in this work.The tolerance factor of the perovskite structure is increased after FA+substitution,which can effectively improve the phase stability of the perovskite films.Meanwhile,the morphology and crystallinity of the perovskite films are improved.To reduce the non-radiative recombination caused by the surface defects,polymethyl methacrylate(PMMA)is used to passivate the surface of the perovskite films.The C=O bond in PMMA can effectively bind to the undercoordinated Pb2+on the surface of perovskite,resulting in a good defect passivation effect and effective inhibition of non-radiative recombina-tion.Thanks to the improvement of the film morphology caused by FA+cation and the PMMA passivation,a low-thresh-old,15 μJ/cm2 under nanosecond laser excitation is achieved for the red ASE of the Cs0.7FA0.3PbI2Br perovskite film.At the same time,the film has good hydrophobicity and photostability.Under the air humidity environment(RH(40±10)％),the ASE intensity remains at 93％of its initial value after a pulsed laser irradiation of 3 000 μJ/cm2 for 120 min.This work provides a reference for realizing low-threshold and high-stability red ASE and laser.
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