Journal
AGGREGATE
Volume 2, Issue 1, Pages 145-150Publisher
WILEY
DOI: 10.1002/agt2.14
Keywords
intramolecular charge transfer; molecular orientation; organic light-emitting diodes; photophysical switching; phthalonitrile; thermally activated delayed fluorescence
Funding
- JSPS KAKENHI [JP19K15651, JP18H02048]
- Hirose Foundation
- Research Foundation for the Electrotechnology of Chubu
- Hoso Bunka Foundation
- Murata Science Foundation
- Cooperative Research Program Network Joint Research Center for Materials and Devices
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A facile strategy for switching luminescent properties between normal fluorescence and thermally activated delayed fluorescence (TADF) is proposed through structural modulation, where two luminophoric molecules, VPN-Ph and VPN-H, are compared. The introduction of phenyl group in VPN-Ph leads to TADF feature, resulting in significantly higher external electroluminescence (EL) quantum efficiency in an organic light-emitting diode (OLED) compared to VPN-H. Phenyl-triggered geometric modulation has a drastic impact on the resulting photophysical and EL properties, leading to TADF on/off switching.
Herein, a facile strategy for switching luminescent properties between normal fluorescence and thermally activated delayed fluorescence (TADF) is presented. Two luminophoric molecules, VPN-Ph and VPN-H, combining phthalonitrile as an electron-accepting core and triphenylamines as electron-donating peripheries with and without two phenyl groups, are newly developed. A comparative study on their structural and photophysical properties is conducted. While non-phenyl VPN-H does not exhibit TADF but normal fluorescence, phenyl-introduced VPN-Ph exhibits TADF with a high photoluminescence quantum yield as a consequence of the phenyl-triggered steric congestion. By virtue of the TADF feature, an organic light-emitting diode (OLED) incorporating VPN-Ph as an emitter achieves a maximum external electroluminescence (EL) quantum efficiency as high as 28.0%, which is five times higher than that of the VPN-H-based OLED. Thus, phenyl-triggered geometric modulation has a drastic impact on the resulting photophysical and EL properties, leading to TADF on/off switching.
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