Performance Enhancement of Quasi-2D Perovskite Light-Emitting Diodes Based on Phase Control by Volatile Antisolvent Treatment

Quasi-two-dimensional (quasi-2D) perovskites have emerged as promising candidates for high-performance light-emitting diodes (LEDs) due to their unique energy funneling mechanism. However, uncontrollable phase distribution during film crystallization often leads to excessive formation of lower n -phases, which hinder efficient charge transport and radiative recombination. In this study, we demonstrate a facile and effective strategy to modulate the phase distribution and crystallinity of quasi-2D perovskite PEA ₂ (FA _0.7 Cs _0.3 ) _n−1 Pb _n Br _3n+1 thin films using a volatile antisolvent, isopropyl alcohol (IPA). Structural and optical investigations revealed that the IPA treatment effectively suppressed the insulating lower n -phases ( n  < 2) and promoted the growth of higher n -domains ( n  > 3). Optimized IPA treatment of 100 µl yields a high photoluminescence quantum yield and balanced energy funneling, whereas excessive IPA (> 300 µl ) leads to phase oversimplification and morphological defects. Consequently, the green LED fabricated with 100 µl of IPA-treated emissive layer achieved a remarkable peak external quantum efficiency of 19.2% and high luminance, representing a nearly fivefold improvement over the pristine device. This work verifies the critical role of volatile antisolvent engineering in tailoring the energy landscape for high-efficiency perovskite optoelectronics.