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.