An investigation of poly(thienylene vinylene) in organic photovoltaic device

The soluble, conjugated regioregular polymer poly(3-dodecyl-2,5-thienylene vinylene), PDDTV, was synthesized and blended with 1-(3-methoxycarbonyl)propyl-1-phenyl-[6,6]-C-61, PCBM, into bulk heterojunction photovoltaic devices, working toward the goal of being able to tune the spectral response. External quantum efficiency measurements detected a maximum response at 580 nm (coincident with the PDDTV absorption lambda(max)), which corresponds to approximately a 100 nm red-shift as compared to devices made from common MDMO-PPV:PCBM blends. A near linear relationship between the current and light intensity was observed for PDDTV:PCBM devices, with slight deviation at relatively high intensities. Surface topography was investigated by AFM to explore the relationship between the roughness of the film and the device efficiency. The best device performance was observed in a 1:10 PDDTV:PCBM weight ratio and had a power conversion efficiency of 0.24% under AM 1.5G solar illumination conditions. This performance is strongly dependent on the active layer thickness, the thin film morphology, and the PCBM concentration in the film. Further optimization of these conditions is expected to yield PDDTV:PCBM blend devices with significantly improved device performance.