Synthesis, hole mobility, and photovoltaic properties of two alternating poly[3‐(hex‐1‐enyl)thiophene‐co‐thiophene]s

Two alternating poly[3‐(hex‐1‐enyl)thiophene‐co‐thiophene]s, Pa (with 77% trans‐isomer and 23% cis‐isomer) and Pb (with 100% trans‐isomer), were synthesized by the coupling of 2,5‐dibromo‐3‐hex‐1‐enyl‐thiophene to 2,5‐bis(tributylstannyl)thiophene via a Stille reaction and compared with poly(3‐hexylthiophene‐co‐thiophene) (P1) to study the effect of changing the carbon(α)–carbon(β) single bond into a carbon–carbon double bond on the properties of the polymers. From P1 to Pb and to Pa, the ultraviolet–visible absorption peaks of the polymers were slightly redshifted, and their electrochemical bandgaps decreased by 0.05–0.1 eV. X‐ray diffraction analysis indicated that Pa had a better lamellar structure than Pb. The hole mobilities of the three polymers, determined with the space‐charge‐limited current model, were 5.23 × 10−6 (P1), 2.34 × 10−4 (Pb), and 7.02 × 10−4 cm2/V s (Pa). The power conversion efficiencies (PCEs) of polymer solar cells based on the three polymers were 0.87 (P1), 1.16 (Pb), and 1.70% (Pa). The increase in the hole mobility and PCE revealed the important effect of changing the carbon(α)–carbon(β) single bond into a carbon–carbon double bond on the properties of polythiophene derivatives containing 3‐alkylthiophene. The strategy used in this work enlarges the thinking to obtain novel, efficient donor polymers for optoelectronic applications.