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ACS Appl Mater Interfaces. 2014 Nov 26;6(22):19477-81. doi: 10.1021/am505280a. Epub 2014 Nov 6.

Dependence of crystallite formation and preferential backbone orientations on the side chain pattern in PBDTTPD polymers.

Author information

1
King Abdullah University of Science and Technology (KAUST) , Thuwal 23955-6900, Saudi Arabia.

Abstract

Alkyl substituents appended to the π-conjugated main chain account for the solution-processability and film-forming properties of most π-conjugated polymers for organic electronic device applications, including field-effect transistors (FETs) and bulk-heterojunction (BHJ) solar cells. Beyond film-forming properties, recent work has emphasized the determining role that side-chain substituents play on polymer self-assembly and thin-film nanostructural order, and, in turn, on device performance. However, the factors that determine polymer crystallite orientation in thin-films, implying preferential backbone orientation relative to the device substrate, are a matter of some debate, and these structural changes remain difficult to anticipate. In this report, we show how systematic changes in the side-chain pattern of poly(benzo[1,2-b:4,5-b']dithiophene-alt-thieno[3,4-c]pyrrole-4,6-dione) (PBDTTPD) polymers can (i) influence the propensity of the polymer to order in the π-stacking direction, and (ii) direct the preferential orientation of the polymer crystallites in thin films (e.g., "face-on" vs "edge-on"). Oriented crystallites, specifically crystallites that are well-ordered in the π-stacking direction, are believed to be a key contributor to improved thin-film device performance in both FETs and BHJ solar cells.

KEYWORDS:

backbone orientation; benzo[1,2-b:4,5-b′]dithiophene; polymer crystallite; side chain; thieno[3,4-c]pyrrole-4,6-dione; π-conjugated polymers

PMID:
25347287
DOI:
10.1021/am505280a

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