Improved efficiency of Organic Light Emitting Diodes by doping of hole transport layer

The electrical doping process in OLED has been investigated by doping of 0.4 wt % of 2,3,5,6- tetrafluoro -7,7’,8,8’-tetracyano-quinodimethane ( F
4−
TCNQ) in hole transport layer (αNPD). The OLED devices with a structure of ITO/pure:doped α-NPD/Ir(ppy)3:CBP/BCP/Alq
3
/LiF/Al were fabricated using this combination of HTL with green emitting electrophosphorescent material Ir(ppy)
3
doped in CBP. The J-V-L characteristics and device efficiencies with and without doping of HTL has been measured. It was found that the doping increases the device current and device efficiency at lower applied voltages.