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ACS Nano. 2017 Mar 28;11(3):3311-3319. doi: 10.1021/acsnano.7b00608. Epub 2017 Mar 13.

In-Situ Formed Type I Nanocrystalline Perovskite Film for Highly Efficient Light-Emitting Diode.

Author information

1
Department of Chemistry, Yonsei University , Seoul 120-749, Korea.
2
Department of Mechanical Engineering and Materials Science, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States.

Abstract

Excellent color purity with a tunable band gap renders organic-inorganic halide perovskite highly capable of performing as light-emitting diodes (LEDs). Perovskite nanocrystals show a photoluminescence quantum yield exceeding 90%, which, however, decreases to lower than 20% upon formation of a thin film. The limited photoluminescence quantum yield of a perovskite thin film has been a formidable obstacle for development of highly efficient perovskite LEDs. Here, we report a method for highly luminescent MAPbBr3 (MA = CH3NH3) nanocrystals formed in situ in a thin film based on nonstoichiometric adduct and solvent-vacuum drying approaches. Excess MABr with respect to PbBr2 in precursor solution plays a critical role in inhibiting crystal growth of MAPbBr3, thereby forming nanocrystals and creating type I band alignment with core MAPbBr3 by embedding MAPbBr3 nanocrystals in the unreacted wider band gap MABr. A solvent-vacuum drying process was developed to preserve nanocrystals in the film, which realizes a fast photoluminescence lifetime of 3.9 ns along with negligible trapping processes. Based on a highly luminescent nanocrystalline MAPbBr3 thin film, a highly efficient green LED with a maximum external quantum efficiency of 8.21% and a current efficiency of 34.46 cd/A was demonstrated.

KEYWORDS:

high efficiency; light-emitting diode; nanocrystal; perovskite; type I band alignment

PMID:
28278375
DOI:
10.1021/acsnano.7b00608

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