We report the synthesis and photovoltaic properties of poly[2,7-(9,
7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PSiF-DBT). The polymer heterojunction solar cells fabricated from PSiF-DBT as the electron
donor blended with [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as the electron acceptor exhibited a high powerconversion
efficiency up to 5.4% with an open-circuit voltage of 0.90 V, a short-circuit current density of 9.5 mA cm-2
and a fill factor of 50.7% under the illumination of AM 1.5 G from a solar simulator (800 W m-2). A comparative study
between PSiF-DBT and its polyfluorene analogous PFDTBT and PFO-DBT demonstrates that the high performance of
PSiF-DBT originated from its red-shifted absorption spectrum up to 680 nm and high mobility of 1 × 10-3 cm2 V-1 s-1 compared with 645 nm and 3 × 10-4 cm2
V-1 s-1 for corresponding polyfluorene derivatives, respectively. These results indicate polysilafluorene derivatives are a promising new class of donor materials for polymer solar cells.
The photoluminescence (PL) and electroluminescence (EL) properties of two series of novel silole-containing polyfuorenes were comparatively investigated. The band gaps of the copolymers could be tuned by structural designing of siloles and control of molar ratios of the siloles in the copolymers. The copolymers showed strong intra- and inter-molecular energy transfer in the solid state, from which the blue emission from polyfluorene could be suppressed and green and red EL devices based on the two series of copolymers could be achieved. Photovoltaic cell and field effect transistor properties of some copolymers were also evaluated.