Synthesis and characterization of a novel thermally stable silane-based host material for blue phosphorescent organic light-emitting diodes

We report a novel thermally stable host material, namely, bis[3-(2-indolo[3,2,1-jk]carbazolyl)phenyl)diphenylsilane (Si-IDCz), for use in blue phosphorescent organic light-emitting diodes (PhOLEDs). Here, Si-IDCz exhibits a high glass transition temperature (Tg) of 151 °C as it contains a thermally stable silane moiety. Additionally, the rigid silicon core within Si-IDCz effectively suppresses molecular interactions, resulting in a wide bandgap and high triplet energy. Here, we used Si-IDCz as the single host for the blue PhOLEDs. The blue PhOLED with the single-host Si-IDCz exhibited an external quantum efficiency (EQE) of over 15%; an EQE of over 11% was maintained at a high luminance of 5000 cd/m2 owing to the high thermal stability of the Si-IDCz. Furthermore, an improved EQE of more than 20% was achieved by introducing a mixed-host system to enhance the photoluminescence quantum yield; the efficiency roll-off was reduced as well.