title: Highly Efficient Deep Blue Organic Light-Emitting Diodes Based on Imidazole: Significantly Enhanced Performance by Effective Energy Transfer with Negligible Efficiency Roll-off.
abstract: Great efforts have been devoted to develop efficient deep blue organic light-emitting diodes (OLEDs) materials meeting the standards of European Broadcasting Union (EBU) standard with Commission International de L'Eclairage (CIE) coordinates of (0.15, 0.06) for flat-panel displays and solid-state lightings. However, high-performance deep blue OLEDs are still rare for applications. Herein, two efficient deep blue emitters, PIMNA and PyINA, are designed and synthesized by coupling naphthalene with phenanthreneimidazole and pyreneimidazole, respectively. The balanced ambipolar transporting natures of them are demonstrated by single-carrier devices. Their nondoped OLEDs show deep blue emissions with extremely small CIEyof 0.034 for PIMNA and 0.084 for PyINA, with negligible efficiency roll-off. To take advantage of high photoluminescence quantum efficiency of PIMNA and large fraction of singlet exciton formation of PyINA, doped devices are fabricated by dispersing PyINA into PIMNA. A significantly improved maximum external quantum efficiency (EQE) of 5.05% is obtained through very effective energy transfer with CIE coordinates of (0.156, 0.060), and the EQE remains 4.67% at 1000 cd m-2, which is among the best of deep blue OLEDs reported matching stringent EBU standard well.
authors.affiliation: State Key Lab of Supramolecular Structure and Materials, Jilin University , 2699 Qianjin Avenue, Changchun 130012, P. R. China.
authors.forename: Tong
authors.initials: T
authors.lastname: Shan
authors.affiliation: State Key Lab of Supramolecular Structure and Materials, Jilin University , 2699 Qianjin Avenue, Changchun 130012, P. R. China.
authors.forename: Yulong
authors.initials: Y
authors.lastname: Liu
authors.affiliation: State Key Lab of Supramolecular Structure and Materials, Jilin University , 2699 Qianjin Avenue, Changchun 130012, P. R. China.
authors.forename: Xiangyang
authors.initials: X
authors.lastname: Tang
authors.affiliation: State Key Lab of Supramolecular Structure and Materials, Jilin University , 2699 Qianjin Avenue, Changchun 130012, P. R. China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Bai
authors.affiliation: State Key Lab of Supramolecular Structure and Materials, Jilin University , 2699 Qianjin Avenue, Changchun 130012, P. R. China.
authors.forename: Yu
authors.initials: Y
authors.lastname: Gao
authors.affiliation: State Key Lab of Supramolecular Structure and Materials, Jilin University , 2699 Qianjin Avenue, Changchun 130012, P. R. China.
authors.forename: Zhao
authors.initials: Z
authors.lastname: Gao
authors.affiliation: State Key Lab of Supramolecular Structure and Materials, Jilin University , 2699 Qianjin Avenue, Changchun 130012, P. R. China.
authors.forename: Jinyu
authors.initials: J
authors.lastname: Li
authors.affiliation: State Key Lab of Supramolecular Structure and Materials, Jilin University , 2699 Qianjin Avenue, Changchun 130012, P. R. China.
authors.forename: Jian
authors.initials: J
authors.lastname: Deng
authors.affiliation: State Key Lab of Supramolecular Structure and Materials, Jilin University , 2699 Qianjin Avenue, Changchun 130012, P. R. China.
authors.forename: Bing
authors.initials: B
authors.lastname: Yang
authors.affiliation: State Key Lab of Supramolecular Structure and Materials, Jilin University , 2699 Qianjin Avenue, Changchun 130012, P. R. China.
authors.forename: Ping
authors.initials: P
authors.lastname: Lu
authors.affiliation: Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology , Guangzhou 510640, P. R. China.
authors.forename: Yuguang
authors.initials: Y
authors.lastname: Ma
keywords: OLEDs; ambipolar; deep blue; efficiency roll-off; energy transfer