In situ fabrication of perovskite nanocrystals with Dion–Jacobson phase for high-performance blue light-emitting diodes

Blue perovskite light-emitting diodes (PeLEDs) based on pure bromide compositions exhibit notable potential attributed to their stable performance and the absence of halogen phase separation. Nevertheless, a considerable challenge persists in the effective suppression of narrow-bandgap emission phases to ensure optimal color purity. In this investigation, we delve into the utilization of zwitterionic β-alanine (β-Ala) to facilitate the formation of nanocrystalline-structured perovskite. β-Ala, possessing both amino and carboxyl groups, is an effective passivating agent for various defect sites on the perovskite's surface, exhibiting versatility through multiple binding modes. This irregular passivation pattern strategically hinders the perovskite from adopting a conventional quasi-2D layered structure. Through the strategic implementation of diamine ligands and CsBr to modulate the growth process, we successfully engineered quasi-2D perovskite nanocrystals with Dion–Jacobson phase (Q-2D PNCs) via an in situ coordination process. The application of the PNCs as emitters in blue PeLEDs yielded promising outcomes. The pure blue PeLED with electroluminescent peak at 473 nm achieves a maximum brightness and external quantum efficiency (EQE) of 8005 cd/m2 and 8.91%, respectively. Additionally, PeLEDs with sky blue emission (479 nm) exhibited a maximum brightness and EQE of 9431 cd/m2 and 10.02%, respectively.