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Title: Molecular organization in MAPLE-deposited conjugated polymer thin films and the implications for carrier transport characteristics

Abstract

The morphological structure of poly(3-hexylthiophene) (P3HT) thin films deposited by both Matrix Assisted Pulsed Laser Evaporation (MAPLE) and solution spin-casting methods are investigated. We found that the MAPLE samples possessed a higher degree of disorder, with random orientations of polymer crystallites along the side-chain stacking, π-π stacking, and conjugated backbone directions. Furthermore, the average molecular orientations and relative degrees of crystallinity of MAPLE-deposited polymer films are insensitive to the chemistries of the substrates onto which they were deposited; this is in stark contrast to the films prepared by the conventional spin-casting technique. In spite of the seemingly unfavorable molecular orientations and the highly disordered morphologies, the in-plane charge carrier transport characteristics of the MAPLE samples are comparable to those of spin-cast samples, exhibiting similar transport activation energies (56 meV versus 54 meV) to those reported in the literature for high mobility polymers.

Authors:
 [1];  [1];  [2];  [3];  [1]
  1. Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Materials Science and Engineering
  2. Argonne National Lab. (ANL), Argonne, IL (United States). X-ray Science Division
  3. Univ. of Houston, TX (United States). Dept. of Chemical and Biomolecular Engineering
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF); Vietnam Education Foundation
OSTI Identifier:
1339946
Grant/Contract Number:
AC02-06CH11357
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Polymer Science. Part B, Polymer Physics
Additional Journal Information:
Journal Volume: 55; Journal Issue: 1; Journal ID: ISSN 0887-6266
Publisher:
Wiley
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; conjugated polymers; ellipsometry; MAPLE; thin film transistor; X-ray

Citation Formats

Dong, Ban Xuan, Li, Anton, Strzalka, Joseph, Stein, Gila E., and Green, Peter F. Molecular organization in MAPLE-deposited conjugated polymer thin films and the implications for carrier transport characteristics. United States: N. p., 2016. Web. doi:10.1002/polb.24237.
Dong, Ban Xuan, Li, Anton, Strzalka, Joseph, Stein, Gila E., & Green, Peter F. Molecular organization in MAPLE-deposited conjugated polymer thin films and the implications for carrier transport characteristics. United States. doi:10.1002/polb.24237.
Dong, Ban Xuan, Li, Anton, Strzalka, Joseph, Stein, Gila E., and Green, Peter F. 2016. "Molecular organization in MAPLE-deposited conjugated polymer thin films and the implications for carrier transport characteristics". United States. doi:10.1002/polb.24237. https://www.osti.gov/servlets/purl/1339946.
@article{osti_1339946,
title = {Molecular organization in MAPLE-deposited conjugated polymer thin films and the implications for carrier transport characteristics},
author = {Dong, Ban Xuan and Li, Anton and Strzalka, Joseph and Stein, Gila E. and Green, Peter F.},
abstractNote = {The morphological structure of poly(3-hexylthiophene) (P3HT) thin films deposited by both Matrix Assisted Pulsed Laser Evaporation (MAPLE) and solution spin-casting methods are investigated. We found that the MAPLE samples possessed a higher degree of disorder, with random orientations of polymer crystallites along the side-chain stacking, π-π stacking, and conjugated backbone directions. Furthermore, the average molecular orientations and relative degrees of crystallinity of MAPLE-deposited polymer films are insensitive to the chemistries of the substrates onto which they were deposited; this is in stark contrast to the films prepared by the conventional spin-casting technique. In spite of the seemingly unfavorable molecular orientations and the highly disordered morphologies, the in-plane charge carrier transport characteristics of the MAPLE samples are comparable to those of spin-cast samples, exhibiting similar transport activation energies (56 meV versus 54 meV) to those reported in the literature for high mobility polymers.},
doi = {10.1002/polb.24237},
journal = {Journal of Polymer Science. Part B, Polymer Physics},
number = 1,
volume = 55,
place = {United States},
year = 2016,
month = 9
}

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  • Although spin casting and chemical surface reactions are the most common methods used for fabricating functional polymer films onto substrates, they are limited with regard to producing films of certain morphological characteristics on different wetting and nonwetting substrates. The matrix-assisted pulsed laser evaporation (MAPLE) technique offers advantages with regard to producing films of different morphologies on different types of substrates. Here, we provide a quantitative characterization, using X-ray diffraction and optical methods, to elucidate the additive growth mechanism of MAPLE-deposited poly(3-hexylthiophene) (P3HT) films on substrates that have undergone different surface treatments, enabling them to possess different wettabilities. We show thatmore » MAPLE-deposited films are composed of crystalline phases, wherein the overall P3HT aggregate size and crystallite coherence length increase with deposition time. A complete pole figure constructed from X-ray diffraction measurements reveals that in these MAPLE-deposited films, there exist two distinct crystallite populations: (i) highly oriented crystals that grow from the flat dielectric substrate and (ii) misoriented crystals that preferentially grow on top of the existing polymer layers. The growth of the highly oriented crystals is highly sensitive to the chemistry of the substrate, whereas the effect of substrate chemistry on misoriented crystal growth is weaker. The use of a self-assembled monolayer to treat the substrate greatly enhances the population and crystallite coherence length at the buried interfaces, particularly during the early stage of deposition. Furthermore, the evolution of the in-plane carrier mobilities during the course of deposition is consistent with the development of highly oriented crystals at the buried interface, suggesting that this interface plays a key role toward determining carrier transport in organic thin-film transistors.« less
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