Water-induced construction of Cs4PbBr6/CsPbBr3 heterojunction for efficient perovskite light-emitting diode

Perovskite Cs4PbBr6/CsPbBr3 heterojunction with a strongly carrier-confined effect is emerging as a promising luminescent material for perovskite light-emitting diodes (PeLEDs). However, it is a big challenge to construct the heterojunction on a molecular scale to fully excavate this confinement effect for efficient electroluminescence efficiencies of PeLEDs. Herein, we report a water-induced construction of Cs4PbBr6/CsPbBr3 heterojunction for efficient PeLEDs via adding trace water with strong polarity. Benefiting from its strong carrier confinement effect, this heterojunction has a higher exciton binding energy (94.7 meV) and a lower nonradiative decay rate constant (0.007 ns−1) compared to that of single CsPbBr3 nanocrystals (NCs) (14.1 meV and 0.031 ns−1). Based on it, the as-fabricated PeLEDs exhibit a greatly-improved maximum current efficiency of 43.62 cd A−1 and a peak EQE of 11.31%, approximately 1.5 times that of CsPbBr3 NCs (28.43 cd A−1 and 7.78%). Evidently, this work provides an important way toward the construction of Cs4PbBr6/CsPbBr3 heterojunction and then promotes the commercial development of heterojunction-like optoelectronics.