Novel high-performance photovoltaic D-A conjugated polymers bearing 1,2-squaraine moieties as electron-deficient units

Two D-A type conjugated polymers bearing 3,4-dithiophenyl-1,2-squaraine as acceptor segment, thiophene and benzo[1,2-b;4,5-b']dithiophene (BDT) as donor moieties, namely. PTTST and PBDTTST, are synthesized by Stille coupling reaction. Compared with their reference polymer PBDTTT without 1,2-squaraine unit, both PTTST and PBDTTST possess more extended absorption in the vis-NIR region of 600-800 nm and lowered HOMO energy levels of 0.1-0.2 eV. Bulk-heterojunction PSC with PBDTTST as p-type material shows high performance with the best PCE value of 1.26% (V-oc = 0.87 V, J(sc) = 3.81 mA/cm(2), FF = 0.38) under irradiation of 100 mW/cm(2), while that of PBDTTT-based PSC is 0.36%. Therefore, 1,2-squaraine is a promising electron-acceptor component for construction of high performance photovoltaic D-A type conjugated photovoltaic polymers. (c) 2012 Elsevier B.V. All rights reserved.