High-performance polymer heterojunction solar cells of a polysilafluorene derivative

High-performance polymer heterojunction solar cells fabricated from an alternating copolymer of 2,7-silafluorene (SiF) and 4,7-di($2^{\prime }$ -thienyl)-2,1,3-benzothiadiazole (DBT) (PSiF-DBT) as the electron donor blended with [6,6]-phenyl-${\mathrm{C}}_{61}$ -butyric acid methyl ester as the electron acceptor were investigated. A power-conversion efficiency up to 5.4% with an open-circuit voltage of $0.90\mathrm{V}$ , a short-circuit current of $9.5\mathrm{mA}{\mathrm{cm}}^{-2}$ , and a fill factor of 50.7% was achieved under the illumination of AM $1.5\mathrm{G}$ from a calibrated solar simulator $\left(800\mathrm{W}{\mathrm{m}}^{-2}\right)$ . The field-effect transistors fabricated from PSiF-DBT showed a high hole mobility of $\sim 1\times {10}^{-3}{\mathrm{cm}}^2{\mathrm{V}}^{-1}{\mathrm{s}}^{-1}$ .