TY - JOUR
T1 - Use of pyrimidine and pyrazine bridges as a design strategy to improve the performance of thermally activated delayed fluorescence organic light emitting diodes
AU - dos Santos, Paloma Lays
AU - Chen, Dongyang
AU - Pachai Gounder, Rajamalli
AU - Matulaitis, Tomas
AU - Cordes, David Bradford
AU - Slawin, Alexandra Martha Zoya
AU - Jacquemin, Denis
AU - Zysman-Colman, Eli
AU - Samuel, Ifor David William
N1 - Authors are grateful to the Engineering and Physical Sciences Research Council (EPSRC) for support from grants EP/P010482/1 and EP/R035164/1. P. Rajamalli acknowledges support from a Marie Skłodowska-Curie Individual Fellowship (MCIF; No. 749557). Dongyang Chen thanks the China Scholarship Council (grant numbers 201603780001).
PY - 2019/12/4
Y1 - 2019/12/4
N2 - 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 (ΦPL > 68%) and small energy gaps between singlet and triplet excited states (ΔEST < 160 meV). OLEDs using pDTCz-DPmS and pDTCz-DPzS as emitters exhibit blue and green electroluminescence, respectively, with higher maximum external quantum efficiencies (EQEmax of 14% and 18%, respectively) and 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.
AB - 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 (ΦPL > 68%) and small energy gaps between singlet and triplet excited states (ΔEST < 160 meV). OLEDs using pDTCz-DPmS and pDTCz-DPzS as emitters exhibit blue and green electroluminescence, respectively, with higher maximum external quantum efficiencies (EQEmax of 14% and 18%, respectively) and 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.
KW - TADF
KW - Organic light emitting diodes
KW - Pyrimidine
KW - Pyrazine
KW - Blue OLED
KW - Intramolecular hydrogen bond
U2 - 10.1021/acsami.9b16952
DO - 10.1021/acsami.9b16952
M3 - Article
SN - 1944-8244
VL - 11
SP - 45171
EP - 45179
JO - ACS Applied Materials & Interfaces
JF - ACS Applied Materials & Interfaces
IS - 48
ER -