title: Rational design of aggregation-induced emission luminogen with weak electron donor-acceptor interaction to achieve highly efficient undoped bilayer OLEDs.
abstract: In this work, two tailored luminogens (TPE-NB and TPE-PNPB) consisting of tetraphenylethene (TPE), diphenylamino, and dimesitylboryl as a π-conjugated linkage, electron donor, and electron acceptor, respectively, are synthesized and characterized. Their thermal stabilities, photophysical properties, solvachromism, fluorescence decays, electronic structures, electrochemical behaviors, and electroluminescence (EL) properties are investigated systematically, and the impacts of electron donor-acceptor (D-A) interaction on optoelectronic properties are discussed. Due to the presence of a TPE unit, both luminogens show aggregation-induced emission, but strong D-A interaction causes a decrease in emission efficiency and red-shifts in photoluminescence and EL emissions. The luminogen, TPE-PNPB, with a weak D-A interaction fluoresces strongly in solid film with a high fluorescence quantum yield of 94%. The trilayer OLED [ITO/NPB (60 nm)/TPE-PNPB (20 nm)/TPBi (40 nm)/LiF (1 nm)/Al (100 nm)] utilizing TPE-PNPB as a light emitter shows a peak luminance of 49 993 cd m(-2) and high EL efficiencies up to 15.7 cd A(-1), 12.9 lm W(-1), and 5.12%. The bilayer OLED [ITO/TPE-PNPB (80 nm)/TPBi (40 nm)/LiF (1 nm)/Al (100 nm)] adopting TPE-PNPB as a light emitter and hole transporter simultaneously affords even better EL efficiencies of 16.2 cd A(-1), 14.4 lm W(-1), and 5.35% in ambient air, revealing that TPE-PNPB is an eximious p-type light emitter.
authors.affiliation: Guangdong Innovative Research Team, SCUT-HKUST Joint Research Laboratory, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology (SCUT) , Guangzhou 510640, China.
authors.forename: Long
authors.initials: L
authors.lastname: Chen
authors.forename: Yibin
authors.initials: Y
authors.lastname: Jiang
authors.forename: Han
authors.initials: H
authors.lastname: Nie
authors.forename: Rongrong
authors.initials: R
authors.lastname: Hu
authors.forename: Hoi Sing
authors.initials: HS
authors.lastname: Kwok
authors.forename: Fei
authors.initials: F
authors.lastname: Huang
authors.forename: Anjun
authors.initials: A
authors.lastname: Qin
authors.forename: Zujin
authors.initials: Z
authors.lastname: Zhao
authors.forename: Ben Zhong
authors.initials: BZ
authors.lastname: Tang
keywords: aggregation-induced emission; electron donor−acceptor; hole transporter; organic light-emitting diodes; tetraphenylethene