Poly(3-hexylthiophene) formed gels and showed liquid crystalline structures at high concentrations. The absorption properties of poly(3-hexylthiophene) showed dramatic changes during gelation, which is an indication of strong intermolecular pi-electronic coupling of the ordered self-assenibled poly(3-hexylthiophene) gels. The effect of conformational transitions oil the photovoltaic properties of solution-processed poly(3-hexylthiophene)/fullerene blends has been Studied in this Article. It is shown that the photovoltaic performance is strongly affected by gelation, which afters the morphology of the photoactive layer. Device optimization yields solar cells with a power conversion efficiency of 3.78% under standard test conditions (AM 1.5. 100 mW/cm(2)).