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Abstract
Through-space charge-transfer (TSCT) emitters have been extensively explored for thermally activated delayed fluorescence (TADF), but arranging various donors and
acceptors into rigid cofacial conformations for various efficient TSCT TADF emitters has still remained a challenge. Here we report for the first time a “fixing acceptor”
design to reach various efficient TSCT TADF emitters. By chemically fixing the acceptor (benzophenone) with a rigid spiro structure and cofacially aligning various donors with the fixed acceptor, a series of efficient TSCT TADF emitters have been developed. Single-crystal structures and theoretical calculations have verified closely-packed cofacial donor/acceptor conformations and favorable TSCT in the emitters. The emitters afford sky-blue to yellow TADF emission in doped films, with high photoluminescent efficiencies of up to 0.92 and reverse intersystem crossing rates of up to 1.0×106 s−1. Organic light-emitting diodes using the emitters afford sky-blue to yellow electroluminescence with high external quantum efficiencies of up to 20.9%. The work opens a new avenue toward a wide variety of efficient TSCT TADF emitters.
Supplementary materials
Title
Intramolecular Through-Space Charge-Transfer Emitters Featuring Thermally Activated Delayed Fluorescence for High-Efficiency Electroluminescent Devices
Description
Unless otherwise specified, all solvents and reactants were purchased from commercial sources and used as described. 1H and 13C NMR spectra were measured with BRUKER 400/600 MHz NMR spectrometers. Absorption spectra in solution were measured by Macy UV-1800
spectrometer. PL spectra, PL transient lifetimes, phosphorescence spectra at 77 K, and photoluminescent
quantum yields in solution and films were measured using a steady/transient state fluorescence spectrometer (Edinburgh FLS1000) equipped with an integrating sphere. The phosphorescence spectra were measured with a delay time of 9 ms. Cyclic voltammetry was performed on a LK1100 voltammeter in dry CH2Cl2 for oxidation and in dry DMF for reduction (10−3 M), with tetrabutylammonium hexafluorophosphate (0.1 M) and ferrocene as the supporting electrolyte and internal standard, respectively. A glass-carbon plate, a silver wire and a platinum wire were used as the working, reference
and counter electrodes, respectively, and the scan rate was set at 100 mV s−1
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