title: White Polymer Light-Emitting Diodes Based on Exciplex Electroluminescence from Polymer Blends and a Single Polymer.
abstract: In this Article, we designed and synthesized a series of polyfluorene derivatives, which consist of the electron-rich 4,4'-(9-alkyl-carbazole-3,6-diyl)bis(N,N-diphenylaniline) (TPA-Cz) in the side chain and the electron-deficient dibenzothiophene-5,5-dioxide (SO) unit in the main chain. The resulting copolymer PF-T25 that did not comprise the SO unit exhibited blue light-emission with the Commission Internationale de L'Eclairage coordinates of (0.16, 0.10). However, by physically blending PF-T25 with a blue light-emitting SO-based oligomer, a novel low-energy emission correlated to exciplex emerged due to the appropriate energy level alignment of TPA-Cz and the SO-based oligomers, which showed extended exciton lifetime as confirmed by time-resolved photoluminescent spectroscopy. The low-energy emission was also identified in copolymers consisting of SO unit in the main chain, which can effectively compensate for the high-energy emission to produce binary white light-emission. Polymer light-emitting diodes based on the exciplex-type single greenish-white polymer exhibit the peak luminous efficiency of 2.34 cd A(-1) and the maximum brightness of 12 410 cd m(-2), with Commission Internationale de L'Eclairage color coordinates (0.27, 0.39). The device based on such polymer showed much better electroluminescent stability than those based on blending films. These observations indicated that developing a single polymer with the generated exciplex emission can be a novel and effective molecular design strategy toward highly stable and efficient white polymer light-emitting diodes.
authors.affiliation: State Key Laboratory of Luminescent Materials and Devices, and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology , Guangzhou 510640, China.
authors.forename: Junfei
authors.initials: J
authors.lastname: Liang
authors.affiliation: State Key Laboratory of Luminescent Materials and Devices, and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology , Guangzhou 510640, China.
authors.forename: Sen
authors.initials: S
authors.lastname: Zhao
authors.affiliation: State Key Laboratory of Luminescent Materials and Devices, and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology , Guangzhou 510640, China.
authors.forename: Xiao-Fang
authors.initials: XF
authors.lastname: Jiang
authors.affiliation: State Key Laboratory of Luminescent Materials and Devices, and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology , Guangzhou 510640, China.
authors.forename: Ting
authors.initials: T
authors.lastname: Guo
authors.affiliation: State Key Laboratory of Luminescent Materials and Devices, and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology , Guangzhou 510640, China.
authors.forename: Hin-Lap
authors.initials: HL
authors.lastname: Yip
authors.affiliation: State Key Laboratory of Luminescent Materials and Devices, and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology , Guangzhou 510640, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Ying
authors.affiliation: State Key Laboratory of Luminescent Materials and Devices, and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology , Guangzhou 510640, China.
authors.forename: Fei
authors.initials: F
authors.lastname: Huang
authors.affiliation: State Key Laboratory of Luminescent Materials and Devices, and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology , Guangzhou 510640, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Luminescent Materials and Devices, and Institute of Polymer Optoelectronic Materials and Devices, South China University of Technology , Guangzhou 510640, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Cao
keywords: exciplex; highly stable electroluminescence; polymer light-emitting diodes; solution process; white light-emitting