New insight into effect of Molecular Weight in DPP-polymers revealed
© DPP polymer structure © K. SIVULA / 2016 EPFL
Gasperini, Jeanbourquin, and Sivula publish new results in the Journal of Polymer Science on Diketopyrrolopyrrole-Based Polymers in Transistor and Photovoltaic Applications
Uncovering the precise effect of the conjugated polymer chain length on the semiconducting properties in thin-film devices is confounded by the step-growth polymerization techniques typically used. Here, we use preparatory size exclusion chromatography to isolate fractions of two diketopyrrolopyrrolethiophene
based co-polymers with low molar-mass dispersity, -DM, and number average molecular weights up to 180 kDa. We find that the charge carrier mobility can vary over three orders of magnitude in the range from 9 to 70 kDa, while a factor of 3–4 increase in photovoltaic performance was noted over the same
range. The effect of -DM was found to be most drastic when the largest chains were mixed with the shortest. The study of the thin-film morphology and crystallinity by GIWAXS give further insights into the origin of these effects. Link to full text from publisher.