Increased open circuit voltage in a fluorinated quinoxaline-based alternating conjugated polymer

Abstract

A fused ladder D–A type alternating conjugated polymer, PIDT-FQ, with indacenodithiophene (IDT) as the donor unit and di-fluorophenylquinoxaline (FQ) as the acceptor unit, was synthesized and characterized for organic photovoltaic (OPV) application. Optical measurements indicate that the bandgap of PIDT-FQ was 1.81 eV. The incorporation of fluorine allows the polymer to have a desirable highest occupied molecular orbital (HOMO) level (−5.36 eV), which suggested that the polymer would exhibit high open-circuit voltages when blended with fullerene as the electron acceptor. We investigate the morphology and performance of OPV based on blended films of PIDT-FQ and [6,6]-phenyl-C₇₁-butyric acid methyl ester (PC₇₁BM). The resulting fine-scale morphology leads to enhanced performance and a high power efficiency (4.6% under AM 1.5G (100 mW cm⁻²)) when we used the thermal treatment and solvent annealing process.