Unravel the impacts of deep-level defects on auger recombination in nanocrystals for realizing low-threshold blue amplified spontaneous emission

One of the challenges associated with implementing amplified spontaneous emission (ASE) is the significant occurrence of Auger recombination, particularly in the quantum-confined blue emitters. It is well known that quantum confinement exacerbates Auger recombination, while there has been limited exploration of the impact of deep-level defects on Auger recombination. A comprehensive understanding of the influence of defects on multi-body recombination is paramount. This study investigates from a mechanistic perspective how defect-mediated Auger recombination suppresses amplified spontaneous emission. Two representative blue-emissive CsPb(Br x Cl 1-x ) 3 nanocrystals with different deep-level defect states were taken as model systems. We employ time-resolved and temperature-dependent optical characterizations to demonstrate that deep-level defects in the perovskite nanocrystals induce charge separation states because of the ultrafast capture of charge carriers. This process leads to the formation of a charged exciton state and contributes to the Auger recombination under confined conditions, thereby significantly increasing the threshold for population inversion. Leveraging the insight, we achieved pure blue ASE with a record low threshold of 25 μJ cm −2 under a lower deep-level defect density condition. The results highlight the critical role of deep-level defects in Auger recombination, becoming imperative insights for advancing high-performance blue ASE.