Zwitterions Narrow Distribution of Perovskite Quantum Wells for Blue Light-Emitting Diodes with Efficiency Exceeding 15%

While quasi-two-dimensional (quasi-2D) perovskites have emerged as promising semiconductors for light-emitting diodes (LEDs), the broad-width distribution of quantum wells hinders their efficient energy transfer and electroluminescence performance in blue emission. In particular, the underlying mechanism is closely related to the crystallization kinetics and has yet to be understood. Here for the first time, the influence of bifunctional zwitterions with different coordination affinity on the crystallization kinetics of quasi-2D perovskites is systematically investigated. The zwitterions can coordinate with Pb2+ and also act as co-spacer organic species in quasi-2D perovskites, which collectively inhibit the aggregation of colloidal precursors and shorten the distance of quantum wells. Consequently, restricted nucleation of high-n phases and promoted growth of low-n phases are achieved with moderately coordinated zwitterions, leading to the final film with a more concentrated n distribution and improved energy transfer efficiency. It thus enables high-efficiency blue LEDs with a recorded external quantum efficiency of 15.6% at 490 nm, and the operation stability has also been prolonged to 55.3 min. These results provide useful directions for tuning the crystallization kinetics of quasi-2D perovskites, which is expected to lead to high-performance perovskite LEDs.