Novel alternating dioctyloxyphenylene vinylene-benzothiadiazole copolymer: Synthesis and photovoltaic performance

A novel alternating conjugated copolymer (poly [(dioctyloxyphenylene vinylene)-alt-(2,1,3-benzothiadiazole)], C8-PPV-BT) consisting of electron-rich dioctyloxybenzene and electron-deficient 2,1,3-benzothiadiazole repeat units was synthesized via a Pd-catalyzed Heck cross-coupling polycondensation. The thermal, electrochemical, optical properties, and photophysics of C8-PPV-BT blended with [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM) have been investigated. Photovoltaic devices of ITO/PEDOT-PSS/C8-PPV-BT + PCBM (1/4, w/w)/Ba/Al were fabricated and their photovoltaic parameters were measured. The results showed the energy conversion efficiency (17,) and external quantum efficiency (EQE) were 0.335 and 11.7% (451 nm), respectively, under simulated solar light illumination having light intensity of 78.2 mW (.) (cm(2))(-1) (AM1.5), which were both higher than those of devices based on poly [(dioctyloxyphenylene ethynylene)-alt-(2,1,3-benzothiadiazole)] (C8-PPE-BT) and PCBM blend under the same conditions. Optical, electrochemical, and photovoltaic properties of C8-PPV-BT and C8-PPE-BT copolymers were also compared and discussed.