Two-dimensional quinoxaline based low bandgap conjugated polymers for bulk-heterojunction solar cells

Abstract

Two novel two-dimensional quinoxaline derivatives, DTPQx and DTDBPz, based copolymers, P2 and P3, were synthesized through Suzuki polycondensation reaction. Meanwhile, the DPQx based polymer P1 was also designed for comparison. The UV-vis absorptions, thermal stabilities, energy levels, field-effect carrier mobilities and photovoltaic characteristics of these three copolymers were systematically evaluated to understand the relationship between the polymer structure at the molecular level and the photovoltaic performances. Photovoltaic cells based on the two-dimensional quinoxaline-based polymers, P2 and P3, with a structure of ITO/PEDOT:PSS/polymer : PC₇₁BM/Ca/Al exhibited PCEs of over 3% compared to the PCE of less than 2% in the P1-based device.