A series of alternating poly(2,7-carbazole) derivatives have been synthesized. The evaluation of their thermoelectric properties in doped films revealed high electrical conductivity (up to 500 S/cm) and a relatively high Seebeck coefficient (up to 70 μV/K). The best compromise between these two thermoelectric parameters led to a maximum value of 19 μW m−1 K−2 as the power factor. As observed from X-ray analyses, it has been observed that the high electrical conductivity was obtained with structured polymers. Good air stability was also observed with these thermoelectric polymers.

The synthesis and characterization of new heterofluorene derivatives based on germanium are described. These germafluorene monomers have been polymerized with different aromatic comonomers. The resulting homopolymers and alternating copolymers have been characterized by size exclusion chromatography, thermal analyses (TGA and DSC), UV-vis-NIR absorption spectroscopy, X-ray diffraction, and cyclic voltammetry. These homopolymers and copolymers are air-stable and present bandgaps ranging from 3.0 to 1.6 eV. Some copolymers were tested in field-effect transistors (FETs) and bulk heterojunction photovoltaic cells (PCs). Best results in FETs were obtained with poly[2,7-(9,9-di-n-butylgermafluorene)-alt-3,6-bis(thiophen-5-yl)-2,5-dioctylpyrrolo[3,4-]pyrrole-1,4-dione], which shows a hole mobility up to 0.04 cm 2 (V 3 s) -1 with an I on /I off ratio of 1.0 Â 10 6 . For photovoltaic applications, the best results were obtained with poly[2,7-(9,9-di-n-octylgermafluorene)-alt-5,5-(4 0 ,7 0 -di-2-thienyl-2 0 ,1 0 ,3 0 -benzothiadiazole)] with a power conversion efficiency (PCE) of 2.8%.

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