Localized Micro‐Solvent Field Engineering for Efficient and Reproducible Quasi‐Quantum‐Dot Perovskite Light‐Emitting Diodes

Abstract

ABSTRACT Perovskite light‐emitting diodes (PeLEDs) are promising candidates for next‐generation display and lighting technologies. However, conventional strategies for controlling morphology and crystalline structure often face challenges such as inefficient carrier transport and poor batch‐to‐batch reproducibility, primarily due to the presence of long organic ligands and the environment‐sensitive nature of crystallization dynamics. Here, we present a localized micro‐solvent field engineering strategy that simultaneously enhances device efficiency and reproducibility. By applying a nitrogen micro‐gas flow, we obtain a clean nitrogen atmosphere and a lower substrate temperature for subsequent film coating. By incorporating low‐boiling‐point solvent acetonitrile into the precursor solution as a nucleation promoter, we precisely control the nucleation and growth kinetics. This synergistic approach, which avoids chemical hot‐injection synthesis and insulating long‐chain ligands, produces uniform quasi‐quantum‐dot perovskite films with the grain size (7–15 nm) approaching the exciton Bohr diameter with higher exciton binding energy. PeLEDs fabricated using this method demonstrate a peak external quantum efficiency of 33.79%, an average efficiency approaching 31%, excellent batch‐to‐batch consistency, and successful integration in pixel array devices. This strategy not only overcomes critical limitations in efficiency and reproducibility for solution‐processed PeLEDs but also provides a broadly applicable framework to advance the performance and scalability of other perovskite optoelectronic devices.