Strategic regulation of crystallization kinetics to achieve efficient pure-red quasi-2D perovskite light-emitting diodes

Efficient and stable pure-red perovskite light-emitting diodes (PeLEDs) show great potential for high-definition displays. Despite significant advancements in device performance over recent years, achieving both high external quantum efficiency (EQE) and long-term stability remains a significant challenge. In this study, we employed 5-amino valeric acid (5-AVA) as a crystallization agent and utilized in situ analytical techniques, including X-ray diffraction, UV–visible spectroscopy, and photoluminescence, to explore its role in the crystallization kinetics of quasi-2D perovskite (POEA 0.7 NMA 0.3 ) 2 CsPb 2 I 7 films. Our results reveal that the strong coordination capability of 5-AVA with Pb 2+ ions promotes direct nucleation of perovskite phases and slows down crystal growth following a “rapid nucleation, slow growth” mechanism. This well-controlled crystallization kinetics leads to enhanced crystallinity, reduced defect density, and a narrower cascade phase distribution for quasi-2D perovskites. Ultimately, these improvements enable pure-red PeLEDs to achieve higher EQEs, increasing from 15.68 % to 21.23 %, and extending the operational lifetime, from 242 min to 506 min. Our research highlights the potential of precisely regulating crystallization kinetics to address the key challenges of phase impurity and non-radiative energy losses in quasi-2D PeLEDs, paving the way toward reliable and efficient PeLEDs.