Journal
CHEMICAL ENGINEERING JOURNAL
Volume 433, Issue -, Pages -Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.cej.2021.133598
Keywords
Thermally activated delayed fluorescence; Horizontal dipole orientation; Efficiency roll-off; Reverse intersystem crossing; Organic light-emitting diodes
Categories
Funding
- National Natural Science Foundation of China [21805195, 51903160]
- Shenzhen Science and Technology Program [KQTD20170330110107046]
- Science and Technology Innovation Commission of Shenzhen [JCYJ20180507182244027]
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In this study, two novel highly efficient blue thermally activated delayed fluorescence (TADF) materials were synthesized, overcoming the concentration quenching effects and efficiency roll-offs. The synthesized compounds exhibited high horizontal dipole orientation and photoluminescence quantum yields, demonstrating excellent TADF properties and stable emission characteristics. OLEDs based on these compounds achieved high efficiency and brightness.
Highly efficient blue thermally activated delayed fluorescence (TADF) materials with high horizontal dipole orientation (Theta(//)) remain a big challenge due to the concentration quenching effects and serious efficiency roll-offs in their corresponding organic light-emitting diodes (OLEDs). We herein report two novel TADF compounds, namely 2TDBA-SBA and TDBA-SBA, which were facilely synthesized by utilizing a rigid oxygen-bridged cyclized triarylboron-based unit (TDBA) as the acceptor and a spiro acridine (SBA) as the donor. Benefiting from the rigid and planar skeleton of the acceptor and the linear molecular shape, high Theta(//)s and photoluminescence quantum yields (PLQYs) of similar to 90% were achieved. Significantly, TDBA-SBA exhibited excellent TADF properties with a short delayed fluorescence lifetime of only 684 ns and narrow full-width at half-maximum (FWHM) of 44 nm in solution state, accompanied by the high PLQYs of over 80% at high doping concentrations, manifesting the alleviated exciton quenching effects. Consequently, OLEDs based on TDBA-SBA achieved a high maximum external quantum efficiency (EQE) of 29.3% and a maximum brightness of 27663 cd cm(-2). Importantly, an EQE over 20% was realized even at the high brightness of 10000 cd cm(-2), signifying a small efficiency roll-off.
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