Reduced Efficiency Roll-Off and Enhanced Stability in Perovskite Light-Emitting Diodes with Multiple Quantum Wells.

Mixed-formamidinium (FA) and -cesium (Cs) cations were used to fabricate multiple quantum well (MQW) perovskite light-emitting diodes (PeLEDs). The partial substitution of FA with Cs facilitates the formation of wider quantum wells, which can effectively reduce efficiency roll-off by suppressing Auger recombination. The device has a peak external quantum efficiency (EQE) of 7.8% at a current density of 125 mA cm-2, maintaining an EQE of ∼6.6% at a high current density of 500 mA cm-2. Due to the improved stability of mixed-cation structure, we achieve a PeLED device with a lifetime of ∼31 h under a constant current density of 10 mA cm-2.