Unprecedented roll-off ratio in high-performing red TADF OLED emitters featuring 2,3-Indole-annulated naphthalene imide and auxiliary donors
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0000-0003-2807-5840 Date
2024
Journal Title
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Volume Title
Publisher
Royal Society of Chemistry
Abstract
The capability of organic emitters to harvest triplet excitons via a thermally activated delayed fluorescence (TADF) process has opened a new era in organic optoelectronics. Nevertheless, low brightness, and consequently insufficient roll-off ratio, constitutes a bottleneck for their practical applications in the domain of organic light-emitting diodes (OLEDs). To address this formidable challenge, we developed a new design of desymmetrized naphthalimide (NMI) featuring an annulated indole with a set of auxiliary donors on its periphery. Their perpendicular arrangement led to minimized HOMO-LUMO overlap, resulting in a low energy gap (ΔEST – 0.05-0.015 eV) and efficient TADF emission with a photoluminescence quantum yield (PLQY) ranging from 82.8% to 95.3%. Notably, the entire set of dyes (NMI-Ind-TBCBz, NMI-Ind-DMAc, NMI-Ind-PXZ, and NMI-Ind-PTZ) was utilized to fabricate TADF OLED devices, exhibiting yellow to red electroluminescence. Among them, red-emissive NMI-Ind-PTZ, containing phenothiazine as an electron-rich component, revealed predominant performance with a maximum external quantum efficiency (EQE) of 23.6%, accompanied by persistent luminance of 38,000 cd/m². This results in a unique roll-off ratio (EQE10 000 = 21.6%), delineating a straightforward path for their commercial use in lighting and display technologies
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Citation
M. Grzelak, D. Kumar, M. A. Kochman, G. Wiosna-Sayga, M. Morawiak, A. Kubas, P. Data and M. Lindner, Chem. Sci., 2024, DOI: 10.1039/D4SC01391C.