A low band gap co-polymer of dithienogermole and 2,1,3- benzothiadiazole by Suzuki polycondensation and its application in transistor and photovoltaic cells

reduction of steric hindrance between the solubilising alkyl groups and adjacent thiophene rings. The improved crystalline structure of PSBTBT resulted in a higher charge carrier mobility and improved solar cell performance in blends with fullerene derivatives. Low band gap co-polymers containing silafluorene, 40 dithieno[3,2-b:2′,3′-d]silole 7 and silaindacenodithiophene have recently demonstrated promising FET and solar cell performance, with dithienosilole co-polymers exhibiting FET mobilities up to 0.08 cm/Vs and solar cell power conversion efficiencies up to 7.3%. 45 However to date there has been little work on the properties of polymers containing related germanium bridged systems. Germanium sits below silicon in the periodic table, but due to the d-block contraction (or ‘scandide’ contraction), both elements exhibit similar covalent radii, with an average C-Ge 50