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.