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The work includes the development of organic emitters based on naphthalenimide, modified in the 3- and 4-positions with indole, along with a set of twisted electron-rich substituents. The asymmetric arrangement of donor-acceptor units leads to the minimization of HOMO-LUMO overlap, resulting in a low energy gap (ΔEST = 0.05 – 0.015 eV) and effective emission of TADF with high photoluminescence quantum yield (PLQY) ranging from 82.8% to 95.3%. Using our set of emitters, we successfully produce OLED devices that exhibit electroluminescence from yellow to red. The utilization of our most effective NMI-Ind-PTZ emitter in OLEDs demonstrates its high efficiency with EQEmax = 23.6% and red emission (λEL = 613 nm). Moreover, the developed emitters are characterized by high stability, confirmed by the low roll-off ratio (luminance maintained at 10,000 cd/m² with an EQE of 21.6%), making these red TADF OLEDs among the most stable devices (Lmax = 38,319 cd/m²).

M. Grzelak, D. Kumar, M. A. Kochman, G. Wiosna-Sałyga, M. Morawiak, A. Kubas, P. Data, M. Lindner,  „Unprecedented roll-off ratio in high-performing red TADF OLED emitters featuring 2,3-Indole-annulated naphthalene imide and auxiliary donors”, Chem. Sci.