Recent advancements in perovskite light-emitting diodes (PeLEDs) have positioned them as a frontier research area in optoelectronics, offering transformative potential for display technologies through exceptional traits such as high color purity and tunable emission wavelengths. State-of-the-art pure-iodine PeLEDs have achieved external quantum efficiencies (EQEs) exceeding 30%, marking a milestone toward efficient light emitters. However, these high-performance devices typically emit in the near-infrared spectrum, diverging from the visible range critical for display applications. Red-emitting PeLEDs in the 620–650 nm (pure red) and 650–700 nm (deep red) wavelength ranges have yet to reach comparable efficiency levels, leaving room for improvement.
A critical hurdle to device performance lies in defects within solution-processed perovskite thin films. Halide vacancies, prevalent in metal halide perovskites due to their low formation energies, are known to induce ionic migration, leading to nonradiative recombination and film degradation. Common strategies to mitigate these defects involve incorporating additives with functional groups (e.g., P═O, S═O) to passivate Pb²⁺ dangling bonds. However, these additives often remain embedded in the perovskite lattice, introducing complexity and new challenges, including lattice distortion, structural degradation, and reduced thermal stability from residual organic components.
Researchers Zhang Xingwang, You Jingbi, and colleagues from the Institute of Semiconductors, Chinese Academy of Sciences, have pioneered a defect-passivation approach that avoids introducing foreign elements or groups. By integrating volatile I₂ as an additive, they create an iodine-rich environment, elevating the formation energy of iodine vacancies. I₂ also dissociates into free I⁻ ions, reducing vacancy density. This method modifies the perovskite’s surface energy, regulating crystallization kinetics to enhance crystallinity and vertical alignment of organic spacers, facilitating charge carrier transport. Employing this strategy, the team fabricated deep-red (678 nm) and pure-red (649 nm) PeLEDs with maximum EQEs of 32.5% and 29.5%, respectively—setting new benchmarks for reported performance in these color ranges.
This innovation underscores a promising pathway toward high-efficiency, color-tunable PeLEDs for next-generation displays, balancing defect suppression with structural integrity.
