Pyridine-functionalized carbazole donor and benzophenone acceptor design for thermally activated delayed fluorescence emitters in blue organic light-emitting diodes

Rajamalli Pachai Gounder; Diego Rota Martir; Eli Zysman-Colman

doi:10.1117/1.JPE.8.032106

5 March 2018 Pyridine-functionalized carbazole donor and benzophenone acceptor design for thermally activated delayed fluorescence emitters in blue organic light-emitting diodes

Rajamalli Pachai Gounder, Diego Rota Martir, Eli Zysman-Colman

Author Affiliations +

Funded by: European Research Council (ERC), Leverhulme Trust, Engineering and Physical Sciences Research Council (EPSRC)

Journal of Photonics for Energy, Vol. 8, Issue 3, 032106 (March 2018). https://doi.org/10.1117/1.JPE.8.032106

Abstract

We report a molecular design approach for blue-emitting thermally activated delayed fluorescence (TADF) molecules. The two TADF emitters, (4-(3,6-di(pyridin-3-yl)-9H-carbazol-9-yl)phenyl)(phenyl)methanone (3PyCzBP) and (4-(3,6-diphenyl-9H-carbazol-9-yl)phenyl)(phenyl)methanone (4PyCzBP), possess a pyridine-functionalized carbazole donor and a benzophenone acceptor. Both compounds show broad charge-transfer emission in dichloromethane with a λmax at 497 nm and a photoluminescence quantum yield, ϕPL, of 56% for 3PyCzBP and a λmax at 477 nm and a ϕPL of 52% for 4PyCzBP. The ϕPL decreased to 18% and 10%, respectively, for 3PyCzBP and 4PyCzBP in the presence of O2 confirming that triplet states involved in emission. The poly(methyl methacrylate) (PMMA)-doped (10 wt. %) films show blueshifted emission with λmax at 450 and 449 nm for 3PyCzBP and 4PyCzBP, respectively. The maximum ϕPL of 23.4% is achieved for these compounds in PMMA-doped film. The difference in energy between the singlet and triplet excited states (ΔEST) is very small at 0.06 and 0.07 eV for 3PyCzBP and 4PyCzBP, respectively. Multilayer organic light-emitting diode devices fabricated using these molecules as emitters show that the maximum efficiency (EQEmax) of the blue devices is 5.0%.

Citation Download Citation

Rajamalli Pachai Gounder, Diego Rota Martir, and Eli Zysman-Colman "Pyridine-functionalized carbazole donor and benzophenone acceptor design for thermally activated delayed fluorescence emitters in blue organic light-emitting diodes," Journal of Photonics for Energy 8(3), 032106 (5 March 2018). https://doi.org/10.1117/1.JPE.8.032106

Received: 8 November 2017; Accepted: 2 February 2018; Published: 5 March 2018

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