Synthesis and Photovoltaic Properties of a Poly(2,7-carbazole) Derivative Based on Dithienosilole and Benzothiadiazole

A low bandgap poly(2,7‐carbazole) derivative PCDSBT containing dithienosilole and benzothiadiazole is synthesized by Stille polymerization. The incorporation of dithienosilole and carbazole causes PCDSBT to have a broad absorption from 350 to 800 nm and a relatively low HOMO level. Solar cell devices fabricated by blending PCDSBT with [6,6]‐phenyl‐C61‐butyric acid methyl ester (PC61BM) at a 1:2 weight ratio in a mixed solvent of 3% (by volume), 1,8‐diiodooctane, and 97% dichlorobenzene lead to a power conversion efficiency of 1.65% under the illumination of AM 1.5G (100 mW · cm−2). A poly(2,7‐carbazole) derivative PCDSBT with dithienosilole and benzothiadiazole is designed and synthesized. PCDSBT has a narrow bandgap and a relatively low HOMO level. A power conversion efficiency of 1.65% is achieved for this polymer when 1,8‐diiodooctane is used as an additive.