In this paper, the driving mechanism of carrier-generated organic field-effect transistors (OFETs) with pentacene and vanadium pentoxide (V(2)O(5)) layers is discussed. In this study, large on-currents were observed in an OFET with a 35-mm V(2)O(5) layer. Devices with aluminum (Al)/pentacene/V(2)O(5)/Al layer structures were also prepared. These devices exhibited a large current density in spite of their high carrier injection barriers between each layer and the Al electrodes. Moreover, new absorption bands corresponding to the radical cation absorption of pentacene were observed within the absorption spectrum of the pentacene and V(2)O(5) mixed layers. It was inferred that the charge transfer (CT) complexes that formed at the interface between the pentacene and V(2)O(5) layers were dissociated by the applied gate voltage and that the generated holes contributed to driving the OFETs.