The authors report that the poly(3-hexylthiophene-2,5-diyl) (P3HT) nanogratings shaped by nanoimprint lithography show enhanced hole mobility and strong anisotropy of conductance due to nanoimprint-induced three-dimensional polymer chain alignment. Field effect transistors were fabricated using these nanogratings and device measurements show a hole mobility of 0.03 cm(2)/V s along the grating direction, which is about 60 times higher than that of nonoptimized thin film transistors. Organic photovoltaic devices (OPV) were made using the P3HT nanograting with infiltration of [6,6]-phenyl-C61-butyric acid methyl ester. Compared to similar bilayer and bulk heterojunction devices, the nanoimprinted OPV shows improved device performance. (C) 2010 American Vacuum Society. [DOI:10.1116/1.3501343]