structurally isomeric carbazole/triazole (TAZ)-based bipolarhost materials 1–4 were designed and synthesized. These new materials were found to exhibit wide energy gaps (Eg: 3.29–3.52 eV), high triplet energies (ET: 2.56–2.76 eV), high thermal stability (Td: 426–454 °C), high glass-transition temperatures (Tg: 116–156 °C) and excellent film-forming property. Green and blue emitting devices with fac-tris(