Synthesis And Properties Of Polythiophene Derivatives With Elcctron-drawing Groups In The Side Chains

Harvesting energy from sunlight using photovoltaic cells is an important solution to the growing energy crisis. Organic solar cells have attracted much attention as light weight, low cost and potential large-area. So far, the highest power-conversion efficiency of the organic solar cell reaches10.7%.The linear D-A low-bandgap polymers exhibited excellent properties. The absorption band and carrier mobility of the resultant conjugated copolymers could be fine-tuned by changing the acceptors in the side chains. We have designed and synthesized the polymers with electron-drawing groups in the side chains.We have successfully designed and synthesized the polymer of PDTS-NCN and the polymer of PDTS-CN.In this study, copolymers that consist of dithienosilole as electron-donating unit and4-Nitrophenylacetonitrile (or n-Butyl cyanoacetate) as electron-accepting moieties were synthesized by Stille coupling reaction. The polymer PDTS-NCN exhibit bad solubility, so we designed and synthesized another polymer PDTS-CN, the polymer show good solubility at room temperature in organic solvents such as tetrahydrofuran, dichlormethane, and chlorobenzene.We studied the photovoltaic properties of the polymer PDTS-CN. The UV-vis absorption spectrum was acquired in tetrahydrofuran solution and solid state as thin film. HOMO and LUMO energy levels of the polymer was estimated from cyclic voltammograms of polymer thin film drop-cast from tetrahydrofuran solution and calculated from the oxidative potential and reductive potential respectively. In the polymer solution, the sharp absorption peaks are327nm,400nm and498nm; in the solid state, the sharp absorption peaks are330nm,408nm and516nm; the HOMO and LUMO energy levels are respectively-5.25eV and-3.21eV.Preliminary studies suggest that the2-D polymers will be promising donors.