Optoelectronic Properties of Alternating Copolymers Based on 3,4-Ethylenedioxythiophene and Various Dibromoarenes and Organic Solar Cells Prepared Thereof

High molecular weight π-conjugated alternating copolymers were obtained by direct arylation polycondensation of 3,4-ethylenedioxythiophene (EDOT) with various dibromoarenes in the presence of a solid-supported palladium catalyst, PITS (palladium immobilized on thiol-modified silica gel). The counter part of the EDOT unit controlled the electrochemical HOMO and LUMO levels of the polymers. The existence of a diketopyrroropyrole electron-acceptor unit and/or a bithiophene electron-donor unit strongly affected HOMO and LUMO levels and their band gap. Poly(EDOT-alt-dithienyldiketopyrrolopyrole), PEDOTDPT, exhibited the narrowest electrochemical HOMO-LUMO band gap (1.15 eV) and an extremely wide light absorption region. An organic solar cell made with PEDOTDPT, [ITO/PEDOT:PSS/PEDOTDPT:PC61BM/Ca/Al/], showed an efficiency of 0.20%.