This paper presents the investigation of a donor-acceptor copolymer of 3-hexylthiophene and benzothiadiazole (PDHTBT) to generate macroscopically oriented nanofibers by self-assembly approach to be used as an active layer for organic field effect transistor (OFET). Aligned polymeric nanofibers with long range order was confirmed by various microscopic techniques and XRD analyses. OFET containing aligned nanofibers (Si/SiO2/ PDHTBT/Ag) exhibited an impressive field effect mobility of 2.29 +/- 0.85 cm(2)/V.s with an ON/OFF ratio of similar to 10(5) and a low threshold voltage of - 0.47 +/- 0.05 V at room temperature which relies on the texture and domains generated in the film. Light induced enhancement in charge transport owing to the formation of photo-induced charge carriers postures a facile strategy for the fabrication of high performing plastic electronic devices.