White organic light-emitting diodes based on emission from DPVBi-doped 4,48-bis (2,28-diphenylvinyl)-1, 18-biphenyl

Abstract

White organic light-emitting diodes were fabricated by using 4, 48-bis (2, 28-diphenylvinyl)-1, 18-biphenyl (DPVBi) as a dopant with a structure of ITO/4,4’-bis[N-(1-naphthyl-1-)-N-phenyl-amino]-biphenyl (NPB, 50 nm)/NPB:DPVBi (molecular weight ratio 10:1,30 nm)/tris-(8-hydroxyquinoline)aluminum (Alq₃, 20 nm)/LiF(1 nm)/Al. A broad emissive band with four major peaks of 438, 464, 496 and 520 nm was obtained by electroluminescence spectra, of which 438 nm-, 464 nm- and 520 nm-peak come from emission of NPB, DPVBi and Alq₃, respectively, and 496 nm-one resulted from the emissive superposition of three materials above. The emission from DPVBi was attributed to the charge trapping from NPB. The emission region was transferred partly from Alq₃ to DPVBi-doped NPB by introducing the dopant DPVBi, which leads to emission of DPVBi and an enhanced emission from NPB. The maximum luminance and current efficiency were 4721 cd/m² at 22 V and 0.80 cd/A at 5V, respectively.

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