Using an Organic Molecule with Low Triplet Energy as a Host in a Highly Efficient Blue Electrophosphorescent Device

To achieve high efficiencies in blue phosphorescent organic light-emitting diodes (PhOLEDs), the triplet energies (T-1) of host materials are generally supposed to be higher than the blue phosphors. A small organic molecule with low singlet energy (S-1) of 2.80eV and triplet energy of 2.71eV can be used as the host material for the blue phosphor, [bis(4,6-difluorophenylpyridinato-N,C-2)iridium(III)] tetrakis(1-pyrazolyl)borate (FIr6; T-1=2.73eV). In both the photo- and electro-excited processes, the energy transfer from the host material to FIr6 was found to be efficient. In a three organic-layer device, the maximum current efficiency of 37cdA(-1) and power efficiency of 40LmW(-1) were achieved for the FIr6-based blue PhOLEDs.