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This content will become publicly available on October 2, 2018

Title: Critical Role of Surface Energy in Guiding Crystallization of Solution-Coated Conjugated Polymer Thin Films

It is well-known that substrate surface properties have a profound impact on morphology of thin films solution coated atop and the resulting solid-state properties. However, design rules for guiding the substrate selection have not yet been established. Such design rules are particularly important for solution coated semiconducting polymers, as the substratedirected thin film morphology can impact charge transport properties by orders of magnitude. We hypothesize that substrate surface energies dictate the thin film morphology by modulating the free energy barrier to heterogeneous nucleation. To test this hypothesis, we systematically vary the substrate surface energy via surface functionalization techniques. We perform in-depth morphology and device characterizations to establish the relationship between substrate surface energy, thin film morphology and charge transport properties, employing a donor-accepter (D-A) conjugated polymer. Here, we find that decreasing the substrate surface energy progressively increases thin film crystallinity, degree of molecular ordering and extent of domain alignment. Notably, the enhanced morphology on the lowest surface energy substrate lead to a 10-fold increase in the charge carrier mobility. We further develop a free energy model relating the substrate surface energy to the penalty of heterogeneous nucleation from solution in the thin film geometry. The model correctly predicts the experimentalmore » trend, thereby validating our hypothesis. This work is a significant step towards establishing design rules and understanding the critical role of substrates in determining morphology of solution coated thin films.« less
Authors:
 [1] ;  [1] ;  [2] ;  [3] ; ORCiD logo [2] ; ORCiD logo [1]
  1. Univ. of Illinois, Urbana, IL (United States). Dept. of Chemical and Biomolecular Engineering
  2. Purdue Univ., West Lafayette, IN (United States). Dept. of Chemistry
  3. Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS), X-ray Science Division
Publication Date:
Grant/Contract Number:
AC02-06CH11357; 1641854
Type:
Accepted Manuscript
Journal Name:
Langmuir
Additional Journal Information:
Journal Volume: 34; Journal Issue: 3; Journal ID: ISSN 0743-7463
Publisher:
American Chemical Society
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC); National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Thin Films
OSTI Identifier:
1418274