Improving the Luminous Efficiency of Organic Light Emitting Diodes using a Modulated Doping Hole Injection Layer

Modulated doping of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane (F4-TCNQ) in a hole injection layer (HIL) of 4,4',4"-tris(N-3-methylphenyl-N-phenyl-amino)-triphenylamine (m-MTDATA) was investigated. The device fabricated with an indium-tin-oxide (ITO)/ m-MTDATA:chi% F4-TCNQ/N'-di(naphthalen-1-yl)-N,N'-diphenyl-benzidine (NPB)/tris-(8-hydroxyquinolinato) aluminum(III) (Alq3)/LiF/Al structure was optimized by adjusting the doping concentration and region in HIL to enhance device's efficiency and luminance. 4, 7-diphenyl-1, 10-phenanthroline (BPhen) is used as a hole blocking layer (HBL). Moreover, F4-TCNQ is inserted in the m-MTDATA to study the emission characteristics of OLEDs. The OLED having an efficiency up to 12 cd/A is achieved in the study