Solvent Doping of PEDOT/PSS: Effect on Terahertz Optoelectronic Properties and Utilization in Terahertz Devices

Yan, Fei; Parrott, Edward P. J.; Ung, Benjamin S.-Y.; Pickwell‐MacPherson, Emma

doi:10.1021/acs.jpcc.5b00465

Cited by 66 publications

(49 citation statements)

References 32 publications

(51 reference statements)

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“…The Drude–Smith model basically assumes that phase coherence is completely lost after a series of collisions. Supposing persistence of velocity after the first collision (single‐scattering approximation) the complex dielectric function of the Drude–Smith model reduces to

ϵ true(ω true) = ϵ_{\infty} - \frac{ω_{p}^{2}}{ω^{2} + i ω ω_{τ}} [1 + c_{1} \frac{ω_{normalτ}}{true(ω_{τ} - i ω true)}]

where ω p is the plasma frequency, ω τ is the damping rate, and c 1 represents for the carrier's initial velocity that is retained after experiencing a collision. The parameter c 1 can vary between 0 and −1.…”

Section: Thz Measurements and Drude–smith Modelingmentioning

confidence: 99%

Dielectric Properties of DMSO‐Doped‐PEDOT:PSS at THz Frequencies

Xuan

et al. 2017

Physica Status Solidi (b)

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Poly(3,4‐ethylenedioxythiophene):poly(4‐styrenesulfonate) (PEDOT:PSS) is a promising candidate for terahertz (THz) metamaterial devices. Its dielectric properties can be changed by the dopant dimethylsulfoxide (DMSO). In this study, the dielectric properties of DMSO‐doped‐PEDOT:PSS films are investigated using terahertz time‐domain spectroscopy (THz‐TDS) measurements. The values of the carrier density and mobility are also determined by fitting the dielectric permittivity to the Drude–Smith model. A simple THz frequency selective surface (FSS) is designed based on these DMSO‐doped‐PEDOT:SS films. Strong band rejection can be achieved at resonant frequencies. These results may inspire the development of new materials for manipulating THz waves in future studies.

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ϵ true(ω true) = ϵ_{\infty} - \frac{ω_{p}^{2}}{ω^{2} + i ω ω_{τ}} [1 + c_{1} \frac{ω_{normalτ}}{true(ω_{τ} - i ω true)}]

Section: Thz Measurements and Drude–smith Modelingmentioning

confidence: 99%

Dielectric Properties of DMSO‐Doped‐PEDOT:PSS at THz Frequencies

Xuan

et al. 2017

Physica Status Solidi (b)

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“…The optical conductivity of most ECPs deviates from Drude behavior in the longer wavelength range, especially in the range of a few to tens of THz. 16,22,25,51 The most striking deviation is the appearance of a peak in the real optical conductivity in the FIR or MIR ranges followed by reduced conductivity for vanishing frequencies (illustrated in Fig. 1(a)).…”

Section: Previous Modifications Of the Drude Model Applied To Ecpsmentioning

confidence: 99%

“…23 On the contrary, results from THz time-domain spectroscopy (THz-TDS) indicated a relatively flat dispersion in the THz range for highly conductive ECPs. 16,51 The DS model instead modifies the Drude model by considering successive charge carrier collisions with (immobile) ions. 17 In this model, the carrier velocity after each collision reduces (scales) by a parameter C n , where n denotes the number of collisions.…”

Section: Previous Modifications Of the Drude Model Applied To Ecpsmentioning

confidence: 99%

“…As example, the DS model has been reported to overestimate charge mobility and underestimate carrier density. 16,51 In addition, neither the LMD nor the DS model account for molecular vibrations, which are important features that contribute to the optical conductivity of organic materials. Although some research implied that molecular vibrations are of minor importance, deviation between experimental data and model fits indicates that not accounting for molecular vibrations may lead to erroneous determination of the charge carrier properties (as the molecular vibration contributions to the optical conductivity may then instead be casted into the carrier transport).…”

Section: Previous Modifications Of the Drude Model Applied To Ecpsmentioning

confidence: 99%

“…As model ECP system, we use thin films of poly [3,4-ethylenedioxythiophene] (PEDOT), which is the most widely used ECP for organic electronic devices, owing to its attractive optical and electrical properties. 16,22,36,[44][45][46][47][48][49][50][51][52][53] More specifically, we employed vapor phase polymerization (VPP) to synthesize thin films of highly conductive PEDOT:tosylate (PEDOT:Tos, where tosylate is the counterion balancing the charge). 54 VPP PEDOT:Tos typically has a high degree of order and has been reported to exhibit semi-metallic behavior, making it further more attractive for a comprehensive frequency-dependent optical conductivity study.…”

Section: Introductionmentioning

confidence: 99%

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On the anomalous optical conductivity dispersion of electrically conducting polymers: ultra-wide spectral range ellipsometry combined with a Drude–Lorentz model

et al. 2019

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Electrically conducting polymers (ECPs) are becoming increasingly important in areas such as optoelectronics, biomedical devices, and energy systems. Still, their detailed charge transport properties produce an anomalous optical conductivity dispersion that is not yet fully understood in terms of physical model equations for the broad range optical response. Several modifications to the classical Drude model have been proposed to account for a strong non-Drude behavior from terahertz (THz) to infrared (IR) ranges, typically by implementing negative amplitude oscillator functions to the model dielectric function that effectively reduce the conductivity in those ranges. Here we present an alternative description that modifies the Drude model via addition of positive-amplitude Lorentz oscillator functions. We evaluate this so-called Drude-Lorentz (DL) model based on the first ultra-wide spectral range ellipsometry study of ECPs, spanning over four orders of magnitude: from 0.41 meV in the THz range to 5.90 eV in the ultraviolet range, using thin films of poly(3,4-ethylenedioxythiophene):tosylate (PEDOT:Tos) as a model system. The model could accurately fit the experimental data in the whole ultrawide spectral range and provide the complex anisotropic optical conductivity of the material. Examining the resonance frequencies and widths of the Lorentz oscillators reveals that both spectrally narrow vibrational resonances and broader resonances due to localization processes contribute significantly to the deviation from the Drude optical conductivity dispersion. As verified by independent electrical measurements, the DL model accurately determines the electrical properties of the thin film, including DC conductivity, charge density, and (anisotropic) mobility. The ellipsometric method combined with the DL model may thereby become an effective and reliable tool in determining both optical and electrical properties of ECPs, indicating its future potential as a contact-free alternative to traditional electrical characterization.Fig. 4 (a) In-plane real optical conductivity dispersion of PEDOT:Tos represented by multiple Lorentz oscillators (the Drude contributions are removed) derived from the DL model. (b) The contributions of the real optical conductivity from THz (blue curve), broad oscillators (brown curve), interband transitions (green curve), and molecular vibrations (grey curves) are indicated. (c and d) Display the amplitude and broadening parameters for each Lorentz oscillator as well as their resonance energy (frequency).Their out-of-plane counterparts are shown in Fig. S10 (ESI †). The parameters for these Lorentz oscillators are listed in Table S2 (ESI †).

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