An unsymmetrical thermally activated delayed fluorescence emitter enables orange-red electroluminescence with 31.7% external quantum efficiency
Journal
Materials Horizons
Journal Volume
8
Journal Issue
8
Pages
2286-2292
Date Issued
2021
Author(s)
Abstract
The thermally activated delayed fluorescence (TADF) emitters based on donor-acceptor (D-A) configuration were continuously developed in the past few years, whereas an unsymmetrical TADF emitter with A-D-A′ configuration has never been reported. Herein, an A-D-A′ type TADF emitter of TRZ-SBA-NAI was firstly developed by simultaneously integrating 2-phenyl-1H-benzo[de]isoquinoline-1,3(2H)-dione and 2,4,6-triphenyl-1,3,5-triazine acceptors into a spirobiacridine donor core. Due to the coexistence of double charge-transfer excited states, TRZ-SBA-NAI displayed dual emission containing a dominant orange-red emission and an anti-Kasha's rule sky-blue emission shoulder in solution. As doped into the host matrix, TRZ-SBA-NAI only exhibited an orange-red emission, together with a high photoluminescence quantum yield of 87%. The linear molecular shape imparted TRZ-SBA-NAI with a high horizontal dipole ratio of 88%. As a result, the TRZ-SBA-NAI based devices achieved a record-high external quantum efficiency of 31.7% with an electroluminescence peak at 593 nm. This finding not only enriches the diversity in TADF molecular design, but also unlocks the huge potential of A-D-A′ type TADF emitters for excellent device performance. ? The Royal Society of Chemistry.
Subjects
Charge transfer
Citrus fruits
Efficiency
Electroluminescence
Fluorescence
Steel beams and girders
Charge-transfer excited state
Device performance
External quantum efficiency
Horizontal dipoles
Molecular design
Molecular shapes
Photoluminescence quantum yields
Thermally activated delayed fluorescences
Quantum efficiency
SDGs
Type
journal article