Synthesis and characterization of conjugated polymers with main-chain donors and pendent acceptors for dye-sensitized solar cells

Abstract

Herein, we report three conjugated polymers with main-chain donors and pendent π-acceptors as photosensitizers for dye-sensitized solar cells (DSSCs). The polymer PPTZF (which contains a phenothiazine (PTZ) chromophore and has a 9,9-dioctyl-fluorene (F) group as the donor unit in the main chain and a cyanoacrylic acid acceptor in the side chain, linked by a thiophene unit) was used as a basic structure. Then 9,9-dioctyl-carbazole (CZ) and triphenylamine (TPA) were selected to replace F and PTZ, respectively, as structural modifications to get another two polymers: PPTZCZ and PTPACZ. Finally, we fabricated devices and examined the effects of different donors with flexible alkyl chains on the photovoltaic performance of DSSCs. Our studies have revealed that the PTPACZ dye, which has a degree of polymerization (DP) of ∼4, exhibited excellent photovoltaic performance with a relatively high power conversion efficiency of 4.4% under standard (Global Air Mass 1.5) illumination. Charge extraction and transient photovoltage decay measurements have demonstrated that the charge recombination lifetime (τ) is a crucial influencing factor on the open-circuit voltage of these polymer dyes.