The hole-injecting structure of 15 nm MoO3-doped 4,4-N,N-bis [N-1-naphthyl-N-phenyl-amino]biphenyl (NPB:MoO3)/5 nm MoO3-doped 4,4′-N,N′-dicarbazole-biphenyl (CBP:MoO3) has been used in organic light emitting diodes (OLEDs). It was found that a device using the 15 nm NPB:MoO3/5 nm CBP:MoO3/NPB combination was superior to one adopting the 20 nm NPB:MoO3/NPB combination due to two major causes: the NPB:MoO3/CBP:MoO3 interface is a quasi-ohmic contact, and the hole transport barrier from CBP:MoO3 to NPB is smaller than that from NPB:MoO3 to NPB; moreover, it outperformed the device employing the 20 nm CBP:MoO3/NPB combination, mostly because of the higher conductivity of NPB:MoO3 compared to CBP:MoO3. We demonstrate that using a structure resulting from uniting two p-doped hole transporters is a beneficial, simple method of achieving an improved trade-off between high conductivity and small hole transport barrier, thereby leading to a significantly reduced ohmic loss in the hole current conduction in the OLEDs, relative to the single p-doped layers.