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Molecular Packing of High-Mobility Diketo Pyrrolo-Pyrrole Polymer Semiconductors with Branched Alkyl Side Chains

Xinran Zhang, Lee J. Richter, Dean M. DeLongchamp, R. Joseph Kline, Matthew R. Hammond, Iain McCulloch, Martin Heeney, Raja S. Ashraf, Jeremy N. Smith, Thomas D. Anthopoulos, Bob Schroeder, Yves H. Geerts, Daniel A. Fischer, and Michael F. Toney, New York (2011)

We describe a series of highly soluble diketo pyrrolo-pyrrole (DPP)-bithiophene copolymers exhibiting field effect hole mobilities up to 0.74 cm2 V1 s1, with a common synthetic motif of bulky 2-octyldodecyl side groups on the conjugated backbone. Spectroscopy, diffraction, and microscopy measurements reveal a transition in molecular packing behavior from a preferentially edge-on orientation of the conjugated plane to a preferentially face-on orientation as the attachment density of the side chains increases. Thermal annealing generally reduces both the face-on population and the misoriented edge-on domains. The highest hole mobilities of this series were obtained from edge-on molecular packing and in-plane liquid-crystalline texture, but films with a bimodal orientation distribution and no discernible in-plane texture exhibited surprisingly comparable mobilities. The high hole mobility may therefore arise from the molecular packing feature common to the entire polymer series: backbones that are strictly oriented parallel to the substrate plane and coplanar with other backbones in the same layer.

Partners : ICL and ULB

Place of Publication : New York

Date of Publication : 2011/08/04

Additional Data : J. Am. Chem. Soc. 2011, 133, 15073–15084

Link to the online version of the article.