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

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.