Achieving Low Threshold and High Optical Gain Amplified Spontaneous Emission in MAPbI₃ Perovskite Films via Symmetric Waveguide Effect

Abstract Lead halide perovskites are attractive light source candidates for new amplifiers and lasers in the growing field of short‐distance data communication. However, the presence of plenty of defects and poor stability are the major obstacle to the production and application of perovskite optoelectronic devices. Three strategies are proposed to prepare MAPbI₃ perovskite films with high stability and enhanced light amplification in this study: 1) MAPbI₃ films are prepared with ionic liquid methylammonium acetate (MAAc) to improve the quality of the films; 2) a poly(methyl methacrylate) (PMMA) passivation layer is used to improve the optical and thermal stability of the MAPbI₃ film; 3) a symmetric waveguide (SWG) structure is designed to enhance the amplified spontaneous emission (ASE) properties of the MAPbI₃ film. The formed SWG exhibits increased mode confinement and reduced propagation loss, thus enabling a lower ASE threshold, a higher optical gain and improved photostability, thermal and humidity stability compared with the pristine MAPbI₃ film. Femtosecond transient absorption spectroscopy and electric field distribution calculation are utilized to elucidate the carrier dynamics and carrier‐phonon effect and the microscopic origin of the observed effects of functionalization. This study indicates the possibility of simple and effective approaches for realizing efficient ASE and lasing.