Identification of the local electrical properties of crystalline and amorphous domains in electrochemically doped conjugated polymer thin films

Maddali, Hemanth; House, Krystal L.; Emge, Thomas J.; O’Carroll, Deirdre M.

doi:10.1039/d0ra02796k

Cited by 13 publications

(18 citation statements)

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“…A recent study on the semiconducting polymer P3HT, containing both amorphous and crystalline domains, showed that chemical doping tends to soften the crystalline domains. [31] The doped crystalline domains in P3HT show a reduced modulus, and their co-existence with amorphous domains in the film causes the spatial modulus histogram in doped P3HT to show a double peak feature. [31] C14-PBTTT films have large semicrystalline terraces, and when chemically doped, shows a spatial modulus histogram that has a single peak.…”

Section: Peakforce Qnm Based Nanomechanical Characterizationmentioning

confidence: 99%

“…[31] The doped crystalline domains in P3HT show a reduced modulus, and their co-existence with amorphous domains in the film causes the spatial modulus histogram in doped P3HT to show a double peak feature. [31] C14-PBTTT films have large semicrystalline terraces, and when chemically doped, shows a spatial modulus histogram that has a single peak. Figure 4a shows a comparison of the spatial modulus measured on a pristine C14-PBTTT film compared with a C14-PBTTT film that was chemically doped to high conductivities up to 1000 S cm −1 using an ion exchange based doping process (see Section S5, Supporting Information).…”

Section: Peakforce Qnm Based Nanomechanical Characterizationmentioning

confidence: 99%

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Mechanical Properties of Organic Electronic Polymers on the Nanoscale

Panchal

Dobryden

Hangen

et al. 2021

Adv Elect Materials

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electronic polymers, have played a pivotal role in the development of flexible and printed electronics over the last two decades. [1][2][3] Composed from rings and chains of carbon atoms, these materials sport a low mass density, as well as electronic, optical, and mechanical properties that are tailored through the chemical design of their constituent molecular units. Weak inter-chain van der Waals bonding within thin films of stacked conjugated organic polymers renders them soft, with intrinsically low Young's moduli several orders of magnitude smaller than conventional inorganic semiconductors such as silicon. [4] These mechanical properties, coupled with a conjugated organic polymer's ability to transport both charges and ions through their matrix, have expanded their use in new research areas such as organic bioelectronics and neural recording. [5][6][7][8][9][10] Organic polymers such as poly(3,4ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) are now a routine choice for flexible microelectrode array implants, [11] and their incorporation is known to improve electrical measurements through lower electrode impedances and higher signal-to-noise ratios. However, a recent nanoscale mechanical characterization of the PEDOT:PSS film elements used in such microelectrode arrays showed local variations over an individual probe, on a length scale of a couple of square micrometers. [12,13] This variation was Organic semiconducting polymers have attractive electronic, optical, and mechanical properties that make them materials of choice for large area flexible electronic devices. In these devices, the electronically active polymer components are micrometers in size, and sport negligible performance degradation upon bending the centimeter-scale flexible substrate onto which they are integrated. A closer look at the mechanical properties of the polymers, on the grain-scale and smaller, is not necessary in large area electronic applications. In emerging micromechanical and electromechanical applicationswhere the organic polymer elements are flexed on length scales spanning their own micron-sized active areas, it becomes important to characterize the uniformity of their mechanical properties on the nanoscale. In this work, the authors use two precision nanomechanical characterization techniques, namely, atomic force microscope based PeakForce quantitative nanomechanical mapping (PF-QNM) and nanoindentation-based dynamical mechanical analysis (nano-DMA), to compare the modulus and the viscoelastic properties of organic polymers used routinely in organic electronics. They quantitatively demonstrate that the semiconducting near-amorphous organic polymer indacenodithiopheneco-benzothiadiazole (C16-IDTBT) has a higher carrier mobility, lower modulus, and greater nanoscale modulus areal uniformity compared to the semiconducting semicrystalline organic polymer poly[2,5-bis(3-tetradecylthiophen-2-yl) thieno[3,2-b]thiophene] (C14-PBTTT). Modulus homogeneity appears intrinsic to C16-IDTBT but can be improved in C14-PBTTT u...

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Section: Peakforce Qnm Based Nanomechanical Characterizationmentioning

confidence: 99%

Section: Peakforce Qnm Based Nanomechanical Characterizationmentioning

confidence: 99%

Mechanical Properties of Organic Electronic Polymers on the Nanoscale

Panchal

Dobryden

Hangen

et al. 2021

Adv Elect Materials

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“…Our previous research concluded that, for e-doped RR-P3HT thin films, dopant concentration is predominantly higher in crystalline domains compared to amorphous ones. 35 Because RRa-P3HT thin films are more amorphous compared to the RR-P3HT thin films, the doping intensity after e-doping is expected to be lower for RRa-P3HT thin films. The lower doping intensity in RRa-P3HT thin films would correspond to lower dopant concentrations, compared to RR-P3HT thin films.…”

Section: ■ Introductionmentioning

confidence: 99%

Dual-Mode Polymer-Based Temperature Sensor by Dedoping of Electrochemically Doped, Conjugated Polymer Thin Films

Maddali

Tyryshkin

O’Carroll

2021

ACS Appl. Electron. Mater.

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Polymer temperature sensors are important for applications in food packaging, air conditioning, wearable devices, and biomedicine. However, the sensing range of these sensors is narrow, and the mode of sensing is restricted to either optical or electrical, which limits their implementation in practice. Here, dual-mode polymer-based temperature sensors are demonstrated with a wide sensing range based on a sensing mechanism that utilizes electrochemically doped (oxidized) regiorandom poly(3-hexylthiophene) (RRa-P3HT). When subjected to temperature, the electrochemically doped RRa-P3HT thin films dedope, resulting in a visible color change from blue (the doped state) to yellow (the dedoped state; similar in color to the pristine film). Energy-dispersive X-ray spectroscopy (EDS) and electron paramagnetic resonance (EPR) spectra show decreases in dopant concentrations with increases in the temperature to which the doped films were subjected, indicating a gradual thermal dedoping in the temperature range from 30 to 80 °C. Visible-wavelength absorption spectra of doped films subjected to increasing temperatures depict both doped and dedoped peaks. The ratio of intensities of dedoped to doped peaks exhibits a linear trend between 30 and 75 °C that can be exploited for optical-mode thermal sensing. This temperature-sensing range is the widest of any polymer-based temperature sensor reported to date. A unique aspect of this thermal sensor is that the thermally induced transition between doped and dedoped states for RRa-P3HT films can be translated into an electrical signal as doped films are electrically conducting. Two-point probe current measurements show an exponential decrease in the current with increasing in temperature.

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“…Combined with the high charge density required for electrochemical doping, this often yields heterogeneous potential energy landscapes in the OMIEC, where different regions or domains of a single active layer can vary greatly in terms of their electroactivity and charge transport properties. In some cases, heterogeneity occurs over extremely small length scales comprising only a few chromophore segments, which greatly limits the utility of conventional characterization techniques that rely on longer-range order and/or periodicity (e.g., X-ray and scanning probe methods − ) for understanding the doping process. It is therefore necessary to develop new approaches for capturing the dynamic picture underlying electrochemical doping to provide a molecular description of charged states in weakly coupled, structurally irregular, and heterogeneous polymer-electrolyte systems.…”

Section: Introductionmentioning

confidence: 99%

Charge-Transfer Intermediates in the Electrochemical Doping Mechanism of Conjugated Polymers

et al. 2020

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We address the nature of electrochemically induced charged states in conjugated polymers, their evolution as a function of electrochemical potential, and their coupling to their local environment by means of transient absorption and Raman spectroscopies synergistically performed in situ throughout the electrochemical doping process. In particular, we investigate the fundamental mechanism of electrochemical doping in an oligoether-functionalized 3,4propylenedioxythiophene (ProDOT) copolymer. The changes embedded in both linear and transient absorption features allow us to identify a precursor electronic state with charge-transfer (CT) character that precedes polaron formation and bulk electronic conductivity. This state is shown to contribute to the ultrafast quenching of both neutral molecular excitations and polarons. Raman spectra relate the electronic transition of this precursor state predominantly to the C β -C β stretching mode of the thiophene heterocycle. We characterize the coupling of the CT-like state with primary excitons and electrochemically induced charge-separated states, providing insight into the energetic landscape of a heterogeneous polymer-electrolyte system and demonstrating how such coupling depends on environmental parameters, such as polymer structure, electrolyte composition, and environmental polarity.

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Identification of the local electrical properties of crystalline and amorphous domains in electrochemically doped conjugated polymer thin films

Abstract: The effects of electrochemical doping on the local domain properties of conjugated polymer films are investigated. Nanoscale crystalline domains are most affected by doping and have a higher degree of doping compared to amorphous domains.

Cited by 13 publications

References 58 publications

Mechanical Properties of Organic Electronic Polymers on the Nanoscale

Mechanical Properties of Organic Electronic Polymers on the Nanoscale

Dual-Mode Polymer-Based Temperature Sensor by Dedoping of Electrochemically Doped, Conjugated Polymer Thin Films

Charge-Transfer Intermediates in the Electrochemical Doping Mechanism of Conjugated Polymers

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