Thin Film Stoichiometry and Defects Management for Low Threshold and Air Stable Near-Infrared Perovskite Laser.

While significant efforts have been devoted to optimize the thin-film stoichiometry and processing of perovskites for applications in photovoltaic and light-emitting diodes, there is a noticeable lack of emphasis on tailoring them for lasing applications. In this study, it is revealed that thin films engineered for efficient light-emitting diodes, with passivation of deep and shallow trap states and a tailored energetic landscape directing carriers toward low-energy emitting states, may not be optimal for light amplification systems. Instead, amplified spontaneous emission (ASE) is found to be sustained by shallow defects, driven by the positive correlation between the ASE threshold and the ratio of carrier injection rate in the emissive state to the recombination rate of excited carriers. This insight has informed the development of an optimized perovskite thin film and laser device exhibiting a low threshold (≈ 60 µJ cm) and stable ASE emission exceeding 21 hours in ambient conditions.