期刊
ACS APPLIED MATERIALS & INTERFACES
卷 11, 期 48, 页码 45171-45179出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsami.9b16952
关键词
TADF; organic light emitting diodes; pyrimidine; pyrazine; blue OLED; intramolecular hydrogen bond
资金
- Engineering and Physical Sciences Research Council (EPSRC) [EP/P010482/1, EP/R035164/1]
- Marie Sklodowska-Curie Individual Fellowship (MCIF) [749557]
- China Scholarship Council [201603780001]
- Region des Pays de la Loire
- EPSRC [EP/P010482/1, EP/R035164/1] Funding Source: UKRI
- Marie Curie Actions (MSCA) [749557] Funding Source: Marie Curie Actions (MSCA)
We present a study of two isomeric thermally activated delayed fluorescence (TADF) emitters 9,9'-(sulfonylbis(pyrimidine-5,2-diyl))bis(3,6-di-tert-butyl-9H-carbazole) (pDTCz-DPmS) and 9,9'-(sulfonylbis(pyrazine-5,2-diyl))bis(3,6-di-tert-butyl-9H-carbazole) (pDTCz-DPzS). The use of pyrimidine and pyrazine as bridging units between the electron donor and acceptor moieties is found to be advantageous compared to the phenyl- (pDTCz-DPS) and pyridine-based analogues (pDTCz-3DPyS and pDTCz-2DPyS). Conformational modulation of the donor groups as a function of the bridge results in high photoluminescence quantum yields (Phi(PL) > 68%) and small energy gaps between singlet and triplet excited states (Delta E-ST < 160 meV). OLEDs using pDTCz-DPmS and pDTCz-DPzS as emitters exhibit blue and green electroluminescence, respectively, with higher maximum external quantum efficiencies (EQE(max) of 14% and 18%, respectively) and a reduced efficiency roll-off as compared to the reference devices using pDTCz-DPS, pDTCz-3DPyS, and pDTCz-2DPyS as the emitters. Our results provide a more complete understanding on the impact of the bridge structure in D-A-D TADF systems on the optoelectronic properties of the emitter and how the balance between color purity and EQE in the devices can be controlled, advancing the design strategies for TADF emitters.
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