We report the synthesis, characterization, microphase separation, field‐effect charge transport, and photovoltaic properties of regioregular poly(3‐hexylthiophene)‐ b ‐poly(3‐cyclohexylthiophene) (P3HT‐ b ‐P3cHT). Two compositions of P3HT‐ b ‐P3cHT (HcH63 and HcH77) were synthesized with weight‐average molecular weights of 155,500 and 210,800 and polydispersity indices of 1.45 and 1.57, respectively. Solvent‐casted HcH77 was found to self‐assemble into nanowires with a width of 12.5 ± 0.9 nm and aspect ratios of 50–120, as observed by TEM imaging. HcH77 and HcH63 annealed 280 °C were observed by small angle X‐ray scattering (SAXS) and wide angle X‐ray scattering (WAXS) to be microphase‐separated with characteristic length scales of 17.0–21.7 nm. The microphase‐separated domains were shown to be crystalline with interlayer backbone (100) d ‐spacings of 1.69 and 1.40 nm, which correspond to the P3HT and P3cHT blocks, respectively. Field‐effect transistors fabricated from P3HT‐ b ‐P3cHT thin films showed a mobility of holes (0.0019 cm 2 /Vs) which is independent of thermal annealing. Bulk heterojunction solar cells based on HcH77/fullerene (PC 71 BM) blend thin films had a maximum power conversion efficiency of 2.45% under 100 mW/cm 2 AM1.5 solar illumination in air. These results demonstrate that all‐conjugated block copolymers are suitable semiconductors for applications in field‐effect transistors and bulk heterojunction solar cells.
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Wu et al. (2009) studied this question.