Efficient blue fluorescent OLEDs based on a D-π-A emitter with the hybridized localized and charge-transfer state

An anthracene-bridged D-p-A emitter, 4-(10-(4-(4,5-diphenyl-4H-1,2,4-triazol-3-yl)phenyl)anthracen-9-yl)-N,N-diphenylaniline (TAZ-An-TPA) was designed and synthesized, in which 3,4,5-triphenyl-4H-triazole (TAZ), anthracene and triphenylamine (TPA) act as the acceptor, p-bridge and donor, respectively. TAZ-An-TPA shows good thermal and electrochemical stabilities as well as hybridized local and charge transfer (HLCT) excited-state properties. The additional TAZ moiety changes the distribution of the frontier molecular orbitals and balances the carrier transport. The doped device based on TAZ-An-TPA emits blue light with a peak at 464 nm and a narrow full width at half maximum of 54 nm. Moreover, the maximum external quantum efficiency (EQE) of the devices reached 8.9%, corresponding to a maximum power efficiency of 11.2 lm W-1 and a current efficiency of 11.5 cd A(-1), which exceeds the theoretical limit of traditional fluorescent devices. These results demonstrate the significant potential of D-p-A emitters with HLCT character in efficient blue OLEDs.