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

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2018, Vol.6 (37), p.9914-9924
• Main Authors: Zhao, Chenyang, Schwartz, Thomas, Stöger, Berthold, White, Fraser J, Chen, Jiangshan, Ma, Dongge, Fröhlich, Johannes, Kautny, Paul
• Format: Article
• Language: English
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/c8tc03537g

Three novel materials ( , and ), based on the indolo[3,2,1- ]carbazole and 9 -carbazole building blocks, with high triplet energies ( > 2.80 eV) and good thermal stability ( > 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- ]carbazole moiety has been developed. The careful molecular design of the title compounds allowed to avoid excimer formation of the indolo[3,2,1- ]carbazole subunits in thin films. Therefore, the improved molecular design broadened the applicability of indolo[3,2,1- ]carbazole host materials and significantly enhanced the efficiency of PhOLED devices based on these derivatives compared to previously reported indolo[3,2,1- ]carbazole based compounds. Accordingly, employing the newly developed materials red (CE : 32.7 cd A , PE : 31.0 lm W , EQE : 20.4%), green (CE : 81.0 cd A , PE : 87.4 lm W , EQE : 21.5%) and blue (CE : 35.5 cd A , PE : 39.9 lm W , EQE : 18.0%) PhOLED devices with a remarkably low efficiency roll-off at 1000 cd m ( - red: 5%; green: 0%; blue: 6%) were fabricated.