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Title: Microstructural Evolution of the Thin Films of a Donor–Acceptor Semiconducting Polymer Deposited by Meniscus-Guided Coating

Abstract

Crucial to the development and refinement of organic electronics is a fundamental understanding of how deposition processes affect the active material’s resulting microstructure in the thin film. Meniscus-guided coating (MGC) methods are attractive because of their amenability to high-throughput, industrially relevant continuous processes like roll-to-roll deposition, but the mechanism of solid film formation has not been elucidated and is valuable for the precise control of thin-film morphology and thus ultimate device performance. Here, in this work, we investigate the microstructural evolution of thin films of a diketopyrrolopyrrole–terthiophene donor–acceptor polymer semiconductor using both in situ and ex situ X-ray diffraction methods. On the basis of a comparison of disorder between the film bulk and the top surface and a depth profiling of the out-of-plane orientation of crystallites, we find that faster coating speeds introduce more disorder into the resulting films because the stochastic nucleation of disordered crystallites at the meniscus air–liquid interface becomes more dominant than substrate-mediated nucleation. Our results suggest that there exist three separate deposition regimes—namely the shear-dominate, disorder-dominate, and Landau–Levich–Derjaguin regimes—revealed by observing both polymer alignment via dry film thickness and optical dichroism, a property sensitive to the flow and shear fields. At low coating speeds, the shearmore » strain imparted upon the solution directly induces polymer alignment, causing an increase in dichroism as a function of coating speed. When solvent evaporation becomes too rapid as coating speeds increase, a decrease in the dichroic ratio is observed before the classical Landau–Levich–Derjaguin regime occurs at the highest coating speeds, resulting in isotropic films. The preservation of out-of-plane crystalline texture throughout the thickness of the films is seen only for lower coating speeds, and a study of different deposition temperatures similarly indicates that the lower overall solvent evaporation is conducive to this process. Increased paracrystalline disorder (i.e., peak broadening) is observed by grazing-incidence wide-angle X-ray diffraction at the top interface of the dry films and at higher coating speeds. Together, these results indicate that more rapid solvent evaporation at higher coating speeds causes increased disorder, which can cause the nucleation of misaligned crystallites, affect the dichroic ratio, and may frustrate the alignment of polymer molecules in the amorphous regions of the film. Finally, because the polymer studied and the deposition technique used are representative models, these results are likely general for aggregating, semicrystalline donor–acceptor polymers deposited with MGC.« less

Authors:
ORCiD logo [1];  [2];  [3];  [4]; ORCiD logo [5];  [5]; ORCiD logo [2]; ORCiD logo [1]
  1. Stanford Univ., CA (United States). Dept. of Chemical Engineering
  2. SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource (SSRL)
  3. Stanford Univ., CA (United States). Dept. of Chemical Engineering; SLAC National Accelerator Lab., Menlo Park, CA (United States). Stanford Synchrotron Radiation Lightsource (SSRL)
  4. BASF Schweiz AG, Basel (Switzerland)
  5. BASF SE, Ludwigshafen (Germany)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
OSTI Identifier:
1461892
Grant/Contract Number:  
AC02-76SF00515; SC0016523
Resource Type:
Accepted Manuscript
Journal Name:
Macromolecules
Additional Journal Information:
Journal Volume: 51; Journal Issue: 11; Journal ID: ISSN 0024-9297
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY

Citation Formats

Shaw, Leo, Yan, Hongping, Gu, Xiaodan, Hayoz, Pascal, Weitz, R. Thomas, Kaelblein, Daniel, Toney, Michael F., and Bao, Zhenan. Microstructural Evolution of the Thin Films of a Donor–Acceptor Semiconducting Polymer Deposited by Meniscus-Guided Coating. United States: N. p., 2018. Web. doi:10.1021/acs.macromol.8b00350.
Shaw, Leo, Yan, Hongping, Gu, Xiaodan, Hayoz, Pascal, Weitz, R. Thomas, Kaelblein, Daniel, Toney, Michael F., & Bao, Zhenan. Microstructural Evolution of the Thin Films of a Donor–Acceptor Semiconducting Polymer Deposited by Meniscus-Guided Coating. United States. doi:https://doi.org/10.1021/acs.macromol.8b00350
Shaw, Leo, Yan, Hongping, Gu, Xiaodan, Hayoz, Pascal, Weitz, R. Thomas, Kaelblein, Daniel, Toney, Michael F., and Bao, Zhenan. Wed . "Microstructural Evolution of the Thin Films of a Donor–Acceptor Semiconducting Polymer Deposited by Meniscus-Guided Coating". United States. doi:https://doi.org/10.1021/acs.macromol.8b00350. https://www.osti.gov/servlets/purl/1461892.
@article{osti_1461892,
title = {Microstructural Evolution of the Thin Films of a Donor–Acceptor Semiconducting Polymer Deposited by Meniscus-Guided Coating},
author = {Shaw, Leo and Yan, Hongping and Gu, Xiaodan and Hayoz, Pascal and Weitz, R. Thomas and Kaelblein, Daniel and Toney, Michael F. and Bao, Zhenan},
abstractNote = {Crucial to the development and refinement of organic electronics is a fundamental understanding of how deposition processes affect the active material’s resulting microstructure in the thin film. Meniscus-guided coating (MGC) methods are attractive because of their amenability to high-throughput, industrially relevant continuous processes like roll-to-roll deposition, but the mechanism of solid film formation has not been elucidated and is valuable for the precise control of thin-film morphology and thus ultimate device performance. Here, in this work, we investigate the microstructural evolution of thin films of a diketopyrrolopyrrole–terthiophene donor–acceptor polymer semiconductor using both in situ and ex situ X-ray diffraction methods. On the basis of a comparison of disorder between the film bulk and the top surface and a depth profiling of the out-of-plane orientation of crystallites, we find that faster coating speeds introduce more disorder into the resulting films because the stochastic nucleation of disordered crystallites at the meniscus air–liquid interface becomes more dominant than substrate-mediated nucleation. Our results suggest that there exist three separate deposition regimes—namely the shear-dominate, disorder-dominate, and Landau–Levich–Derjaguin regimes—revealed by observing both polymer alignment via dry film thickness and optical dichroism, a property sensitive to the flow and shear fields. At low coating speeds, the shear strain imparted upon the solution directly induces polymer alignment, causing an increase in dichroism as a function of coating speed. When solvent evaporation becomes too rapid as coating speeds increase, a decrease in the dichroic ratio is observed before the classical Landau–Levich–Derjaguin regime occurs at the highest coating speeds, resulting in isotropic films. The preservation of out-of-plane crystalline texture throughout the thickness of the films is seen only for lower coating speeds, and a study of different deposition temperatures similarly indicates that the lower overall solvent evaporation is conducive to this process. Increased paracrystalline disorder (i.e., peak broadening) is observed by grazing-incidence wide-angle X-ray diffraction at the top interface of the dry films and at higher coating speeds. Together, these results indicate that more rapid solvent evaporation at higher coating speeds causes increased disorder, which can cause the nucleation of misaligned crystallites, affect the dichroic ratio, and may frustrate the alignment of polymer molecules in the amorphous regions of the film. Finally, because the polymer studied and the deposition technique used are representative models, these results are likely general for aggregating, semicrystalline donor–acceptor polymers deposited with MGC.},
doi = {10.1021/acs.macromol.8b00350},
journal = {Macromolecules},
number = 11,
volume = 51,
place = {United States},
year = {2018},
month = {5}
}

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Figures / Tables:

Figure 1 Figure 1: (top) Deposition regimes demarcated by the trend in optical dichroic ratios as a function of coating speed. Figure adapted from ref. 14 (Copyright 2015 American Chemical Society). (top right) PDPP3T, the polymer studied. (bottom) A schematic of meniscus-guided coating (MGC) highlighting, in the out-of-plane direction, the relative influencemore » of polymer nucleation either at the air-liquid interface or at the substrate surface and their corresponding regime (bottom right). Red ovals indicate crystallites nucleated at the solid-liquid interface, while the blue ovals represent those nucleated from the air-liquid interface.« less

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Works referencing / citing this record:

Impact of the Ink Formulation and Coating Speed on the Polymorphism and Morphology of a Solution‐Sheared Thin Film of a Blended Organic Semiconductor
journal, September 2019

  • Tamayo, Adrián; Riera‐Galindo, Sergi; Jones, Andrew O. F.
  • Advanced Materials Interfaces, Vol. 6, Issue 22
  • DOI: 10.1002/admi.201900950

Bar‐Coated Organic Thin‐Film Transistors with Reliable Electron Mobility Approaching 10 cm 2 V −1 s −1
journal, December 2019

  • Bai, Junhua; Jiang, Yu; Wang, Zhongli
  • Advanced Electronic Materials, Vol. 6, Issue 1
  • DOI: 10.1002/aelm.201901002

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