Use of pyrimidine and pyrazine bridges as a design strategy to improve the performance of thermally activated delayed fluorescence organic light emitting diodes
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Date
04/12/2019Author
Grant ID
EP/P010482/1
EP/R035164/1
749557
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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.
Citation
dos Santos , P L , Chen , D , Pachai Gounder , R , Matulaitis , T , Cordes , D B , Slawin , A M Z , Jacquemin , D , Zysman-Colman , E & Samuel , I D W 2019 , ' Use of pyrimidine and pyrazine bridges as a design strategy to improve the performance of thermally activated delayed fluorescence organic light emitting diodes ' , ACS Applied Materials & Interfaces , vol. 11 , no. 48 , pp. 45171-45179 . https://doi.org/10.1021/acsami.9b16952
Publication
ACS Applied Materials & Interfaces
Status
Peer reviewed
ISSN
1944-8244Type
Journal article
Description
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).Collections
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