High-efficiency conjugated-polymer-hosted blue phosphorescent light-emitting diodes.

Highly-efficient blue phosphorescent light-emitting diodes were fabricated based on a conjugated-polymer host by doping bis(2-(4,6-difluorophenyl)-pyridinato-N,C2′) picolinate (FIrpic) into poly(9,9-dioctylfluorene) (PFO). Previously, conjugated polymers were not considered as potential hosts for blue phosphorescent dyes because of their low-lying triplet energy levels. Energy back transfer would occur and lead to poor luminescent efficiency in both photoluminescence (PL) and electroluminescence (EL) processes. However, by inserting a hole-transporting layer of poly( N-vinylcarbazole) (PVK), the energy back transfer was suppressed. At low FIrpic-doping concentrations, PFO emissions were completely quenched; with 8 wt% FIrpic, a maximum luminous efficiency of 11.5 cd/A was achieved. [ABSTRACT FROM AUTHOR]