Tailoring Ultrafast Energy Funneling and Hot Carrier Cooling in Quasi‐2D Perovskites toward Low‐Threshold Lasing

Abstract Quasi‐2D perovskites exhibit prominent optical properties, including a high exciton binding energy and inherent quantum well configurations, making them highly promising for laser applications. However, their practical implementation in multiple‐quantum‐well lasers is hindered by defect states and heterogeneous phase distributions. Here, it is reported that incorporating carbon dots (CDs) into quasi‐2D perovskites improves crystallinity and phase uniformity, which together reduce trap‐assisted recombination and suppress Auger recombination, facilitating more efficient energy funneling. Theoretical calculations reveal that passivation mechanisms and phase formation kinetics are attributed to the synergistic effects of the multifunctional groups in CDs. A reduction in amplified spontaneous emission (ASE) threshold is achieved in CDs‐mediated quasi‐2D perovskites. Moreover, an optical Kerr‐gating technique is innovatively applied to reveal the microscopic mechanisms governing ASE evolution by elucidating the complex ultrafast carrier dynamics in multiple‐quantum‐well structures. The results indicate that modulation of ultrafast energy funneling and hot carrier cooling enables fine‐tuning of ASE dynamics, providing a strategic pathway for tailoring the gain characteristics toward high‐performance lasing. This paper presents a promising approach to improving quasi‐2D perovskites as gain materials and offers valuable insights into the design of advanced photonic systems by investigating photoexcitation dynamics on ultrafast timescales.