A solution processed p-doped hole transport layer was developed using a poly(9,9'-dioctylfluorene-co-bis-N, N'-(4-ethoxycarbonylphenyl)-bis-N,N'-phenyl benzidine (PFO-co-NEPB) as the hole transport material and 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ) as the p type dopant. The F4-TCNQ doped PFO-co-NEPB layer was insoluble to organic solvent after baking and showed an ohmic contact behavior due to p doping effect of the solution processed F4-TCNQ. Yellow polymer emitting materials could be spin coated on the F4-TCNQ doped PFO-co-NEPB layer, and the driving voltage, power efficiency and lifetime of yellow polymer light-emitting diodes were greatly improved by the F4-TCNQ doping in the PFO-co-NEPB layer. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.004203esl] All rights reserved.