Abstract
Trihalide perovskite semiconductors are emerging as promising emitting materials in light-emitting diodes in view of their low-cost manufacture, solution processing, and high color purity [1]. However, the highest external quantum efficiency reported for perovskite LEDs has so far resided near 14%. The low photoluminescence quantum efficiency of the active layer, and an unbalanced charge injection rate, have until now kept perovskite LEDs performance well below that of the best organic and inorganic LEDs. Here we report visible perovskite LEDs that surpass the 20% quantum efficiency milestone. This stems from a new compositional distribution management strategy that simultaneously provides high luminescence and balanced charge injection. We mix a pre-synthesized CsPbBr3 perovskite with MABr (MA = CH3NH3) additive in the precursor; the different solubility of which yields sequential crystallization into a CsPbBr3@MABr quasi-core-shell structure. The MABr shell passivates nonradiative defects otherwise present in CsPbBr3 crystals, boosting their photoluminescence quantum efficiency; and the MABr capping layer enables balanced charge injection. We document as a result perovskite LEDs whose EQE reaches 20.3%.
© 2018 The Author(s)
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