Title: Comparison of the Mechanical Properties of a Conjugated Polymer Deposited Using Spin Coating, Interfacial Spreading, Solution Shearing, and Spray Coating

Abstract

The mechanical properties of π-conjugated (semiconducting) polymers are a key determinant of the stability and manufacturability of devices envisioned for applications in energy and healthcare. These properties—including modulus, extensibility, toughness, and strength—are influenced by the morphology of the solid film, which depends on the method of processing. To date, the majority of work done on the mechanical properties of semiconducting polymers has been performed on films deposited by spin coating, a process not amenable to the manufacturing of large-area films. Here, we compare the mechanical properties of thin films of regioregular poly(3-heptylthiophene) (P3HpT) produced by three scalable deposition processes—interfacial spreading, solution shearing, and spray coating—and spin coating (as a reference). Our results lead to four principal conclusions. (1) Spray-coated films have poor mechanical robustness due to defects and inhomogeneous thickness. (2) Sheared films show the highest modulus, strength, and toughness, likely resulting from a decrease in free volume. (3) Interfacially spread films show a lower modulus but greater fracture strain than spin-coated films. (4) The trends observed in the tensile behavior of films cast using different deposition processes held true for both P3HpT and poly(3-butylthiophene) (P3BT), an analogue with a higher glass transition temperature. Grazing incidence X-ray diffraction and ultraviolet–visiblemore » spectroscopy reveal many notable differences in the solid structures of P3HpT films generated by all four processes. Herein, while these morphological differences provide possible explanations for differences in the electronic properties (hole mobility), we find that the mechanical properties of the film are dominated by the free volume and surface topography. In field-effect transistors, spread films had mobilities more than 1 magnitude greater than any other films, likely due to a relatively high proportion of edge-on texturing and long coherence length in the crystalline domains. Overall, spread films offer the best combination of deformability and charge-transport properties.« less

Authors:

Choudhary, Kartik  ^[1];

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• Search DOE PAGES for ORCID "0000-0003-2611-8982"

Chen, Alexander X.  ^[1];

• Search DOE PAGES for author "Chen, Alexander X."
• Search DOE PAGES for ORCID "0000-0003-1919-6755"

Pitch, Gregory M. ^[2]; Runser, Rory ^[1]; Urbina, Armando ^[1]; Dunn, Tim J. ^[3]; Kodur, Moses  ^[1];

• Search DOE PAGES for author "Kodur, Moses"
• Search DOE PAGES for ORCID "0000-0002-3890-2945"

Kleinschmidt, Andrew T.  ^[1];

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• Search DOE PAGES for ORCID "0000-0002-6036-6878"

Wang, Benjamin G. ^[1]; Bunch, Jordan A. ^[1]; Fenning, David P.  ^[1];

• Search DOE PAGES for author "Fenning, David P."
• Search DOE PAGES for ORCID "0000-0002-4609-9312"

Ayzner, Alexander L.  ^[2];

• Search DOE PAGES for author "Ayzner, Alexander L."
• Search DOE PAGES for ORCID "0000-0002-6549-4721"

Lipomi, Darren J.  ^[1]

• Search DOE PAGES for author "Lipomi, Darren J."
• Search DOE PAGES for ORCID "0000-0002-5808-7765"

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+ Show Author Affiliations

1. Univ. of California, San Diego, CA (United States)
2. Univ. of California, Santa Cruz, CA (United States)
3. SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource (SSRL)

Publication Date:

Fri Oct 22 00:00:00 EDT 2021

Research Org.:

SLAC National Accelerator Lab., Menlo Park, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES); US Air Force Office of Scientific Research (AFOSR); National Science Foundation (NSF)

OSTI Identifier:

1878574

Grant/Contract Number:  

AC02-76SF00515; FA9550-19-1-0278; DGE-1144086; 1848069; ECCS-1542148

Resource Type:

Accepted Manuscript

Journal Name:

ACS Applied Materials and Interfaces

Additional Journal Information:

Journal Volume: 13; Journal Issue: 43; Journal ID: ISSN 1944-8244

Publisher:

American Chemical Society (ACS)

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; mechanical properties; semiconducting polymers; roll-to-roll deposition; morphology; polymers