Influence of the Hole Blocking Materials on the Luminous Properties of Highly Efficient Blue Organic Light-Emitting Diodes

摘要

Blue organic light emitting diodes (OLEDs) of a multi-layered structure were fabricated and their device performance were investigated. N, N′-bis (1-naphthyl) -N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB) is hole transport and blue light emitter material. We have built some multi-layer structures with hole-blocking layer (HBL). The HBL is inserted between the hole transport layer (HTL) and electron transport layer (ETL) to confine the charge recombination in hole-transporting layer. Three different hole-blocking materials , including BCP (Bathocuproine), TAZ (3-(4-Biphenylyl)-4 -phenyl-5(4-tert-butylphenyl)-1,2,4-triazole), and PBD (2-(4′-tert-bytylphenyl)-5-(4′-diphenyl)-1,3,4- oxadiazole were adopted for comparison. Evidence showned that the BCP hole-blocking material possessed both the superior J-V and L-J characteristics. The superior J-V characteristics was suggested to be due to the BCP film possessing flatter surface morphology. The superior L-J characteristic was deduced to be due to the BCP possessed the smaller barrier height at NPB/BCP for electrons and /or the flatter surface morphology.