Organic blue electrophosphorescence using a cyclic siloxane compound as a host material

In organic blue electrophosphorescence diodes, we used hexaphenylcyclotrisiloxane (DPSiO ₃) as a host material aiming for high efficiency blue electroluminescence (EL). The phosphorescence spectrum of the siloxane compound was measured at T = 77 K in an EPA solution and the results well coincided with those of a benzene solution, indicating that the π-conjugation of DPSiO ₃ is basically localized in a benzene ring. In the OLED devices with DPSiO ₃ as a host, the maximum external EL efficiency of η _ext = 11.1% was obtained with iridium (III) bis (4,6-di-fluorophenyl)-pyridinato-N, C ²) picolinate (FIrpic) as an emitter.