Novel triplet host materials 2,4,6-tris(diarylamino)-1,3,5-triazine derivatives (TRZ1-TRZ4) have been reported and from which TRZ2 as a host for Ir(ppy)(3) was particularly useful in producing high efficiency phosphorescent organic light emitting diodes (OLEDs). This Letter reports the molecular orbital and energy level of these derivatives determined by ab initio calculation. The calculated triplet bandgap energy of TRZ1 has been found to be larger than that of TRZ2 and the TRZ1 molecules and has the lowest dipole moment which infers the highest carrier mobility. Therefore, TRZ1 has the potential to be a superb triplet host material and electron transport material. (c) 2005 Elsevier B.V. All rights reserved.