Aggregation Control, Surface Passivation, and Optimization of Device Structure toward Near‐Infrared Perovskite Quantum‐Dot Light‐Emitting Diodes with an EQE up to 15.4%

Abstract In recent years, the performance of perovskite quantum dots (QDs) and QD‐based light‐emitting diodes (QLEDs) has improved greatly, with electroluminescence (EL) efficiency of green and red emission exceeding 20%. However, the development of perovskite near‐infrared (NIR) QLEDs has reached stagnation, where the reported maximum EL efficiency is still below 6%, limiting their further applications. In this work, new NIR‐emissive FAPbI₃ QDs are developed by post‐treating long alkyl‐encapsulated QDs with 2‐phenylethylammonium iodide (PEAI). The incorporation of PEAI reduces the QD surface defects for giving a high photoluminescence quantum yield up to 61.6%. The n‐octane solution of PEAI‐passivated FAPbI₃ QDs is spin coated on top of the PEDOT:PSS‐treated ITO electrode modified with a thermally crosslinked hole‐transporting layer to give a full‐coverage, smooth, and dense QD film. Incorporating with an effective electron‐transporting material, CN‐T2T, which has deep lowest unoccupied molecular orbital and good electron mobility, the optimal device with EL λ_max at 772 nm achieves an external quantum efficiency up to 15.4% at a current density of 0.54 mA cm⁻² (2.6 V), which is the highest efficiency ever reported for perovskite‐based NIR QLEDs. This study provides a facile strategy to prepare high‐quality perovskite QD films suitable for highly efficient NIR QLED applications.