Insulator to semimetallic transition in conducting polymers

Muñoz, W. A.; Singh, Sandeep Kumar; Franco-González, Juan Felipe; Linares, Mathieu; Crispin, Xavier; Zozoulenko, Igor

doi:10.1103/physrevb.94.205202

Cited by 37 publications

(54 citation statements)

References 52 publications

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“…A schematic illustration of a formation of the band structure in PEDOT thin films is presented in Figure (for details see ref. ). A single undoped PEDOT chain has a band gap around E g ≈ 1.7 eV, see Figure a.…”

Section: Introduction and Formulation Of The Problemmentioning

confidence: 99%

Understanding the Impact of Film Disorder and Local Surface Potential in Ultraviolet Photoelectron Spectroscopy of PEDOT

Muñoz

Crispin

Fahlman

et al. 2017

Macromol. Rapid Commun.

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The spectra of conducting polymers obtained using ultraviolet photoelectron spectroscopy (UPS) exhibit a typical broadening of the tail σ ≈ 1 eV, which by an order of magnitude exceeds a commonly accepted value of the broadening of the tail of the density of states σ ≈ 0.1 eV obtained using transport measurements. In this work, an origin of this anomalous broadening of the tail of the UPS spectra in a doped conducting polymer, PEDOT (poly(3,4-ethylenedioxythiophene)), is discussed. Based on the semiempirical approach and using a realistic morphological model, the density of valence states in PEDOT doped with molecular counterions is computed. It is shown that due to a disordered character of the material with randomly distributed counterions, the localized charge carriers in PEDOT crystallites experience spatially varying electrostatic potential. This leads to spatially varying local vacuum levels and binding energies. Taking this variation into account the UPS spectrum is obtained with the broadening of the tail comparable to the experimentally observed one. The results imply that the observed broadening of the tail of the UPS spectra in PEDOT provides information about a disordered spatially varying potential in the material rather than the broadening of the DOS itself.

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Section: Introduction and Formulation Of The Problemmentioning

confidence: 99%

Understanding the Impact of Film Disorder and Local Surface Potential in Ultraviolet Photoelectron Spectroscopy of PEDOT

Muñoz

Crispin

Fahlman

et al. 2017

Macromol. Rapid Commun.

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show abstract

“…1(e) (only energies above 0.1 eV from the Gaussian mean value are taken into account). Here it may be pointed out that the energy levels associated with neighboring nodes might be correlated because the electrostatic potential around the PEDOT chain is correlated with the positions of the counterions [50,51]. To keep our model on a tractable level we do not account for such correlation because this would require full quantum mechanical calculation over the whole system.…”

Section: (A)mentioning

confidence: 99%

“…However in PEDOT where chains are relatively short, it has been shown that the carriers can be delocalized over one entire single chain [50]. Thus, for simplicity, we choose a spatial position of all nodes in the geometrical centers of corresponding PEDOT chains.…”

Section: (A)mentioning

confidence: 99%

“…The tail of the density of states (DOS) in the valence band can be approximated by the Gaussian with a typical broadening σ ∼ 0.1 eV as shown in Fig. 1(e) [23,50,51].…”

Section: (A)mentioning

confidence: 99%

“…1(e) (for details of the electronic structure of PEDOT:Tos see Refs. [50,51]). A PEDOT doped with negative counterions represents a p-type material where electrical transport is due to the thermally assisted hopping of polarons/bipolarons via the states in the valence band.…”

Section: (A)mentioning

confidence: 99%

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Understanding morphology-mobility dependence in PEDOT:Tos

Rolland

Franco-González

Volpi

et al. 2018

Phys. Rev. Materials

105

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The potential of conjugated polymers to compete with inorganic materials in the field of semiconductor is conditional on fine-tuning of the charge carriers mobility. The latter is closely related to the material morphology, and various studies have shown that the bottleneck for charge transport is the connectivity between well-ordered crystallites, with a high degree of π -π stacking, dispersed into a disordered matrix. However, at this time there is a lack of theoretical descriptions accounting for this link between morphology and mobility, hindering the development of systematic material designs. Here we propose a computational model to predict charge carriers mobility in conducting polymer PEDOT depending on the physicochemical properties of the system. We start by calculating the morphology using molecular dynamics simulations. Based on the calculated morphology we perform quantum mechanical calculation of the transfer integrals between states in polymer chains and calculate corresponding hopping rates using the Miller-Abrahams formalism. We then construct a transport resistive network, calculate the mobility using a mean-field approach, and analyze the calculated mobility in terms of transfer integrals distributions and percolation thresholds. Our results provide theoretical support for the recent study [Noriega et al., Nat. Mater. 12, 1038] explaining why the mobility in polymers rapidly increases as the chain length is increased and then saturates for sufficiently long chains. Our study also provides the answer to the long-standing question whether the enhancement of the crystallinity is the key to designing high-mobility polymers. We demonstrate, that it is the effective π -π stacking, not the long-range order that is essential for the material design for the enhanced electrical performance. This generic model can compare the mobility of a polymer thin film with different solvent contents, solvent additives, dopant species or polymer characteristics, providing a general framework to design new high mobility conjugated polymer materials.

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Flexible Thermoelectric Plastic Via Electrochemistry

Jiang

et al. 2022

Flexible Thermoelectric Polymers and Systems

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Insulator to semimetallic transition in conducting polymers

Cited by 37 publications

References 52 publications

Understanding the Impact of Film Disorder and Local Surface Potential in Ultraviolet Photoelectron Spectroscopy of PEDOT

Understanding the Impact of Film Disorder and Local Surface Potential in Ultraviolet Photoelectron Spectroscopy of PEDOT

Understanding morphology-mobility dependence in PEDOT:Tos

Flexible Thermoelectric Plastic Via Electrochemistry

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