Nanocrystal and Quasi-2D Perovskites Gain Media: From ASE to Laser

Metal halide perovskites have emerged as revolutionary optical gain media, challenging conventional semiconductor lasers with their combination of solution processability, tunable emission, and exceptional optoelectronic properties. This review systematically explores recent advances in perovskite-based amplified spontaneous emission (ASE) and lasing technologies, focusing on low-dimensional systems—nanocrystal (NC) and quasi-two-dimensional (quasi-2D) perovskites. We first elucidate the fundamental photophysical principles governing ASE in these materials, contrasting the quantum confinement-dominated gain in NCs with the exciton funneling mechanism in quasi-2D structures. This is followed by a critical analysis of materials engineering strategies, highlighting how ligand/solvent/additive engineering, phase control, and plasmon coupling work together to suppress nonradiative losses to achieve sub-μJ/cm² ASE thresholds. This paper explores breakthroughs in optically pumped lasers (e.g., room-temperature continuous-wave operation, microcavity integration), as well as ongoing challenges facing electrically pumped devices, including charge injection imbalance and thermal degradation. The review further points to emerging opportunities in scalable synthesis, hybrid-size design, and applications such as on-chip photonics and bioimaging. By correlating molecular-scale defect engineering with macroscopic photonic performance, this study provides a roadmap for developing stable and efficient perovskite coherent light sources, bridging fundamental research with practical applications.