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 λmax 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.