title: In-Situ Formed Type I Nanocrystalline Perovskite Film for Highly Efficient Light-Emitting Diode.
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 PbBr2in precursor solution plays a critical role in inhibiting crystal growth of MAPbBr3, thereby forming nanocrystals and creating type I band alignment with core MAPbBr3by embedding MAPbBr3nanocrystals 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 MAPbBr3thin 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.
authors.forename: Jin-Wook
authors.initials: JW
authors.lastname: Lee
authors.affiliation: Department of Chemistry, Yonsei University , Seoul 120-749, Korea.
authors.forename: Yung Ji
authors.initials: YJ
authors.lastname: Choi
authors.forename: June-Mo
authors.initials: JM
authors.lastname: Yang
authors.affiliation: Department of Chemistry, Yonsei University , Seoul 120-749, Korea.
authors.forename: Sujin
authors.initials: S
authors.lastname: Ham
authors.forename: Sang Kyu
authors.initials: SK
authors.lastname: Jeon
authors.forename: Jun Yeob
authors.identifier: 0000-0002-7677-0605
authors.initials: JY
authors.lastname: Lee
authors.forename: Young-Hyun
authors.initials: YH
authors.lastname: Song
authors.forename: Eun Kyung
authors.initials: EK
authors.lastname: Ji
authors.forename: Dae-Ho
authors.initials: DH
authors.lastname: Yoon
authors.forename: Seongrok
authors.initials: S
authors.lastname: Seo
authors.forename: Hyunjung
authors.initials: H
authors.lastname: Shin
authors.affiliation: Department of Mechanical Engineering and Materials Science, University of Pittsburgh , Pittsburgh, Pennsylvania 15260, United States.
authors.forename: Gil Sang
authors.initials: GS
authors.lastname: Han
authors.forename: Hyun Suk
authors.initials: HS
authors.lastname: Jung
authors.affiliation: Department of Chemistry, Yonsei University , Seoul 120-749, Korea.
authors.forename: Dongho
authors.identifier: 0000-0001-8668-2644
authors.initials: D
authors.lastname: Kim
authors.forename: Nam-Gyu
authors.identifier: 0000-0003-2368-6300
authors.initials: NG
authors.lastname: Park
keywords: high efficiency; light-emitting diode; nanocrystal; perovskite; type I band alignment