Abstract
Computational microscopy based on Martini coarse grained molecular dynamics (MD) simulations of a doped conducting polymer poly(3,4-ethylenedioxythiophene)polystyrene sulfonate (best known as PEDOT:PSS) was performed focussing on the formation of the granular structure and PEDOT crystallites, and the effect of pH on the material morphology. The PEDOT:PSS morphology is shown to be sensitive to the initial distribution of PEDOT and PSS in the solution, and the results of the modelling suggest that the experimentally observed granular structure of PEDOT:PSS can be only obtained if the PEDOT/PSS solution is in the dispersive state in the initial crystallization stages. Variation of the pH is demonstrated to strongly affect the morphology of PEDOT:PSS films, altering their structure between granular-type and homogeneous. It also affects the size of crystallites and the relative arrangement of PEDOT and PSS chains. It is shown that the crystallites in PEDOT:PSS are smaller than those in PEDOT with molecular counterions such as PEDOT:tosylate, which is consistent with the available experimental data. The predicted changes of the PEDOT:PSS morphology with variation of the pH can be tested experimentally, and the calculated atomistic picture of PEDOT:PSS films (not accessible by conventional experimental techniques) is instrumental for understanding the material structure and building realistic models of PEDOT:PSS morphology.
Highlights
Poly(3,4-ethylenedioxythiophene) polymerized in the presence of polystyrene sulfonate (PEDOT:PSS) is one of the most technologically important conducting polymers.[1,2] In contrast to many other conducting polymers, PEDOT:PSS is thermally and chemically stable and is used as an active element in various technological applications including flexible and printable electronic and optical devices, as well as energy storage devices.[3,4,5,6,7,8,9]A massive number of experimental studies have been devoted to investigation of various aspects of the morphology of PEDOT: PSS
The PEDOT:PSS morphology is shown to be sensitive to the initial distribution of PEDOT and PSS in the solution, and the results of the modelling suggest that the experimentally observed granular structure of PEDOT:PSS can be only obtained if the PEDOT/PSS solution is in the dispersive state in the initial crystallization stages
The experimental techniques include electron microscopy such as high-resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM);[13,14,15] diffraction scattering such as grazing incidence wide-angle X-ray scattering (GIWAXS) and grazing-incidence small-angle X-ray scattering (GISAXS);[16,17,18] and photo-electron spectroscopy such as X-ray photoelectron a Department of Physics, Ferdowsi University of Mashhad, Mashhad, Iran b Laboratory of Organic Electronics, Department of Science and Technology, Linkoping University, 60174 Norrkoping, Sweden
Summary
Poly(3,4-ethylenedioxythiophene) polymerized in the presence of polystyrene sulfonate (PEDOT:PSS) is one of the most technologically important conducting polymers.[1,2] In contrast to many other conducting polymers, PEDOT:PSS is thermally and chemically stable and is used as an active element in various technological applications including flexible and printable electronic and optical devices, as well as energy storage devices.[3,4,5,6,7,8,9]. Note that various aspects of morphology and transport in PEDOT doped with molecular counterions (as opposed to PSS, which is a poly-anion) were recently studied by the present authors using all atomistic and coarse-grained molecular dynamics simulations (CG MD), addressing the effect of crystallite formation,[63] the chain length,[62] various counterions and oxidation levels,[18] ion diffusion,[64] and the effect of the substrate on the morphology and conductivity.[65] At the same time, theoretical studies of realistic PEDOT:PSS capturing the essential features of the PEDOT: PSS morphology such as p–p stacking and granular structure formation are practically missing This is remarkable, taking into account the fact that the number of experimental papers on PEDOT:PSS far exceeds 1000 per year and is growing.[11,12] Modeling of a realistic PEDOT:PSS morphology represents a challenging task as compared to PEDOT with molecular counterions, because it requires computation on a length scale exceeding B20 nm in order to describe a granular structure of PEDOT:PSS. Our findings, revealing the effect of the pH on molecular packing, will lead to better understanding of this complex material and hopefully inspire further experimental studies of the effect of pH on the material morphology
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
