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

摘要

Three novel materials (5CzICz, Cz(2)ICz and Cz(3)ICz), based on the indolo[3,2,1-jk] carbazole and 9H-carbazole building blocks, with high triplet energies (E-T 2.80 eV) and good thermal stability (T-g 101 degrees 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, EQE(max): 20.4%), green (CEmax: 81.0 cd A(-1), PEmax: 87.4 lm W-1, EQE(max): 21.5%) and blue (CEmax: 35.5 cd A(-1), PEmax: 39.9 lm W-1, EQE(max): 18.0%) PhOLED devices with a remarkably low efficiency roll-off at 1000 cd m(-2) (Cz(2)ICz - red: 5%; green: 0%; blue: 6%) were fabricated.