Photoluminescence characteristics of organic host materials with wide energy gaps for organic electrophosphorescent devices

The photoluminescence, i.e., fluorescence and phosphorescence, characteristics of host materials with wide energy gaps suitable for phosphorescence-based organic light-emitting diodes (OLEDs) are summarized. In the vacuum deposited films, the host materials show phosphorescent emission in the blue to green region and triplet energy levels of E_T = 2.6-3.1 eV because of the presence of steric hindrance. An OLED containing 1,2,3,4-tetraphenyl-5-(3-pyridyl)benzene as a host and iridium(III) bis[(4,6-difluorophenyl)-pyridinato-N,C²]picolinate as a blue emissive phosphorescent dopant exhibits an external electroluminescence efficiency of ∼12%.