Contact effects have been analyzed, by using numerical simulations, in fully printed p-channel OTFTs based on a pentacene derivative as organic semiconductor and with Au source/drain contacts. Considering source–drain Schottky contacts, with a barrier height of 0.46 eV, device characteristics can be perfectly reproduced. From the detailed analysis of the current density we have shown that current spreading occurs at the source contact, thus influencing the effective contact resistance. At low Vds and for a given Vgs, the current is mainly injected from an extended source contact region and current spreading remains basically constant for increasing Vds. However, by increasing Vds the depletion layer of the Schottky contact expands and reaches the insulator–semiconductor interface, causing the pinch-off of the channel at the source end (Vdsat1). For Vds > Vdsat1 the current injected from the edge of the source …