Synthesis and Characterization of Squaraine-Based Conjugated Polymers With Phenylene Linkers for Bulk Heterojunction Solar Cells

pi-Conjugated copolymers consisting of squaraine dyes as light-harvesting components and phenylene linkers (PSQ) are presented. They show intense absorption in visible (Vis) and near-infrared (NIR) region, originating with the intramolecular charge transfer of the dye. Although their optical and electrochemical properties are dominantly derived from dye components, phenylene linkers affect aggregation in the solid state and phase segregation of the PSQ/PCBM composites. Bulk heterojunction solar cells consisting of PSQ/PCBM exhibit spectral response in VisNIR region, and they show power conversion efficiencies up to 0.64%. The copolymer approach to develop squaraine-based polymers enables the auxiliary tuning of the physical properties that determine photovoltaic performance through the choice of linkers.