Conformational Order in Aggregates of Conjugated Polymers

Journal Article · Wed May 06 00:00:00 EDT 2015 · Journal of the American Chemical Society

DOI:https://doi.org/10.1021/jacs.5b00493· OSTI ID:1392402

Jackson, Nicholas E. ^[1]; Kohlstedt, Kevin L. ^[1]; Savoie, Brett M. ^[1]; Olvera de la Cruz, Monica ^[1]; Schatz, George C. ^[1]; Chen, Lin X. ^[2]; Ratner, Mark A. ^[1]

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1. Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
2. Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States; Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, United States

With the abundant variety and increasing chemical complexity of conjugated poly-friers proliferating the field of organic semiconductors, it has become increasingly important to correlate the polymer molecular structure with its mesoscale conformational and morphological attributes. For instance, it is unknown which combinations of chemical moieties and periodicities predictably produce mesoscale ordering. Interestingly) not all ordered morphologies result in efficient devices. In this work we have parametrized accurate classical force-fields and used these to compute the conformational and aggregation characteristics of single strands of common conjugated polymers. Molecular dynamics trajectories are shown to reproduce experimentally observed polymeric ordering, concluding that efficient organic photovoltaic devices span a range of polymer conformational classes, and suggesting that the solution-phase morphologies have far-reaching effects. Encouragingly, these simulations indicate that despite the wide-range of conformational classes present in successful devices, local molecular ordering, and not long-range crystallinity, appears to be the necessary requirement for efficient devices. Finally, we examine what makes a "good" solvent for conjugated polymers, concluding that dispersive pi-electron solvent-polymer interactions, and not the electrostatic potential of the backbone interacting with the solvent, are what primarily determine a polymer's solubility in a particular solvent, and consequently its morphological characteristics.

• Research Organization: Argonne National Lab. (ANL), Argonne, IL (United States); Energy Frontier Research Centers (EFRC) (United States). Argonne-Northwestern Solar Energy Research Center (ANSER)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
• DOE Contract Number: AC02-06CH11357; SC0001059
• OSTI ID: 1392402
• Journal Information: Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 19 Vol. 137; ISSN 0002-7863
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English