In this article, we would like to demonstrate an electric field annealing method to assist the self-organization of a poly(3-hexylthiophene) (P3HT):[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) hybrid without any thermal post-treatment. By applying a DC electric field perpendicular to the substrate during the solvent-drying process, the formation of fibrous P3HT crystalline domains and phase-separated domains of bulk heterojunctions can be achieved, resulting in a power conversion efficiency (PCE) of over 4%. The grazing incidence X-ray diffraction (GIXRD) measurement suggests that the electric field-assisted annealing will facilitate the crystallization of P3HT in both lamellar stacking and vertical stacking, as a result of improved carrier transport and photovoltaic performance. The method of electric field-assisted annealing can easily be integrated into large-area and low-temperature processes, providing a new route to fabricate low-cost and flexible polymer solar cells.
