Controlling excimer formation in indolo[3,2,1-jk]carbazole/9H-carbazole based host materials for RGB PhOLEDs?

Journal of Materials Chemistry C Pub Date: 2018-08-31 DOI: 10.1039/C8TC03537G

Abstract

Three novel materials (5CzICz, Cz2ICz and Cz3ICz), based on the indolo[3,2,1-jk]carbazole and 9H-carbazole building blocks, with high triplet energies (ET > 2.80 eV) and good thermal stability (Tg > 101 °C) were synthesized, characterized and applied as host materials in PhOLED devices. In course of the preparation of the materials, an improved protocol for the synthesis of the indolo[3,2,1-jk]carbazole moiety has been developed. The careful molecular design of the title compounds allowed to avoid excimer formation of the indolo[3,2,1-jk]carbazole subunits in thin films. Therefore, the improved molecular design broadened the applicability of indolo[3,2,1-jk]carbazole host materials and significantly enhanced the efficiency of PhOLED devices based on these derivatives compared to previously reported indolo[3,2,1-jk]carbazole based compounds. Accordingly, employing the newly developed materials red (CEmax: 32.7 cd A?1, PEmax: 31.0 lm W?1, EQEmax: 20.4%), green (CEmax: 81.0 cd A?1, PEmax: 87.4 lm W?1, EQEmax: 21.5%) and blue (CEmax: 35.5 cd A?1, PEmax: 39.9 lm W?1, EQEmax: 18.0%) PhOLED devices with a remarkably low efficiency roll-off at 1000 cd m?2 (Cz2ICz – red: 5%; green: 0%; blue: 6%) were fabricated.

Graphical abstract: Controlling excimer formation in indolo[3,2,1-jk]carbazole/9H-carbazole based host materials for RGB PhOLEDs
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