Solution-processed p-doped hole-transport layer and its application in organic light-emitting diodes

We investigate p-type doping poly(9-vinylcarbazole) (PVK) hole-transport layer (HTL) with tetrafluoro-tetracyano-quinodimethane introduced via cosolution. We found that the performances of devices with doped HTLs are significantly improved. The efficiency and lifetime of the p-doped device are 2.3 and 3.7 times as large as that of the control device with pure PVK as a HTL. Furthermore, the turn-on voltage of the device is reduced from 9.5 to 3.6 V by using a p-doped HTL. These improved properties are attributed to the formation of the charge-transfer complex in the HTL, which increases hole injection and conductivity of p-doped films considerably.