Controlling the mode of operation of organic transistors through side-chain engineering

Giovannitti, Alexander; Sbircea, Dan Tiberiu; Inal, Sahika; Nielsen, Christian B.; Bandiello, Enrico; Hanifi, David; Sessolo, Michele; Malliaras, George G.; McCulloch, Iain; Rivnay, Jonathan

doi:10.1073/pnas.1608780113

Cited by 394 publications

(661 citation statements)

References 36 publications

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“…Our current findings demonstrate that the CPEs swell less than PEDOT‐based materials, presumably due to the lack of a polyionic phase. Although swelling is limited, the capacitance measured at the oxidation potential is higher for PTHS − TBA + than for PEDOT:PSS, indicating the ease of ion access to the conjugated backbone in the former …”

Section: Resultsmentioning

confidence: 97%

“…We modeled the data using an established equivalent circuit comprising serially connected impedance elements; the resistance of the electrolyte and the impedance of the polymer represented by a resistor and a capacitor, C , in parallel . As the films get doped with the applied bias, the impedance, below 1000 Hz decreases, with an increase in the extracted capacitance values (Figure d and Figure S4, Supporting Information) . The films can be assumed to have bulk doping, therefore, it is reasonable to assume a volumetric interaction of ions with the polymer.…”

Section: Resultsmentioning

confidence: 99%

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Smaller Counter Cation for Higher Transconductance in Anionic Conjugated Polyelectrolytes

Schmidt

ElMahmoudy

Malliaras

et al. 2017

Macro Chemistry & Physics

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Conjugated polyelectrolytes (CPEs) are a focus of research because combine their inherent electrical conductivity and the ability to interact with ions in aqueous solutions or biological systems. However, it is still not understood to what degree the counter ion in CPEs influences the properties of the CPE itself and the performance of electronic transducers. In order to investigate this, three different conjugated polyelectrolytes, poly(6‐(thiophen‐3‐yl)hexane‐1‐sulfonate)s (PTHS−X+), are synthesized, which have the same polythiophene backbone but different X+ counter ions: the bulky tetrabutylammonium (TBA+), tetraethylammonium (TEA+), and the smallest tetramethylammonium (TMA+). At the interface with biological systems, thin CPE films have to be stable in an aqueous environment and should allow the inward and outward flow of ions from the electrolyte. Since the studied PTHS−X+ have different solubilities in water, the optical properties of pristine PTHS−X+ as well as of crosslinked PTHS−X+ via UV–vis absorption spectroscopy are investigated additionally. PTHS−TMA+ exhibits better aggregation, fast interdiffusion of ions, and fast recovery from the oxidized state. Additionally, spectroelectrochemical and cyclic voltammetric as well as electrochemical capacitance investigations show that PTHS−TMA+ can be oxidized to a higher degree. This leads to a better performance of PTHS−TMA+‐based organic electrochemical transistors.

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Section: Resultsmentioning

confidence: 97%

Section: Resultsmentioning

confidence: 99%

Smaller Counter Cation for Higher Transconductance in Anionic Conjugated Polyelectrolytes

Schmidt

ElMahmoudy

Malliaras

et al. 2017

Macro Chemistry & Physics

Self Cite

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“…This volumetric coupling of ions and electrons inside the channel leads to high‐gain OECTs and a simultaneous increase in both the capacitance and the electron mobility of the film . Previous studies have shown that exchanging the hydrophobic, aliphatic side chains of a conjugated backbone with hydrophilic, ethylene glycol (EG) side chains improves the OECT performance . Giovannitti et al reported a series of n‐type random copolymers comprising various EG side chain percentages with respect to alkyl side chains and observed that the reduction potential of the copolymers depends on the percentage of EG side chains where glycol chain percentages of ≥50% are required to operate the copolymer in n‐type OECTs .…”

Section: Introductionmentioning

confidence: 99%

“…This result was attributed to facile ion uptake in the channel due to enhanced swelling of copolymers with high percentage of glycol side chains in aqueous electrolytes . Currently, the top accumulation mode OECT performer (beyond depletion mode OECTs based on PEDOT:PSS derivatives) is the p‐type, hydrophilic conjugated polymer poly(2‐(3,3′‐bis(2‐(2‐(2‐methoxyethoxy)ethoxy)ethoxy)‐[2,2′‐bithiophen]‐5‐yl)thieno [3,2‐b] thiophene) p(g2T‐TT), which shows significantly higher transconductance than its analog with aliphatic chains (p(a2T‐TT)) . While p(g2T‐TT) performed better than p(a2T‐TT), it is unclear whether the performance of p‐type polymers in OECTs scales with the amount of EG side chains.…”

Section: Introductionmentioning

confidence: 99%

Balancing Ionic and Electronic Conduction for High‐Performance Organic Electrochemical Transistors

Savva

Hallani

Cendra

et al. 2020

Adv Funct Materials

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146

239

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Conjugated polymers that support mixed (electronic and ionic) conduction are in demand for applications spanning from bioelectronics to energy harvesting and storage. To design polymer mixed conductors for high‐performance electrochemical devices, relationships between the chemical structure, charge transport, and morphology must be established. A polymer series bearing the same p‐type conjugated backbone with increasing percentage of hydrophilic, ethylene glycol side chains is synthesized, and their performance in aqueous electrolyte gated organic electrochemical transistors (OECTs) is studied. By using device physics principles and electrochemical analyses, a direct relationship is found between the OECT performance and the balanced mixed conduction. While hydrophilic side chains are required to facilitate ion transport—thus enabling OECT operation—swelling of the polymer is not de facto beneficial for balancing mixed conduction. It is shown that heterogeneous water uptake disrupts the electronic conductivity of the film, leading to OECTs with lower transconductance and slower response times. The combination of in situ electrochemical and structural techniques shown here contributes to the establishment of the structure–property relations necessary to improve the performance of polymer mixed conductors and subsequently of OECTs.

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“…It has been shown indeed that hydrophilic side chains favor efficient transport of ions, as compared to hydrophobic (aliphatic) side chains. [26] In addition to these advantages, side chains engineering could facilitate processing of the material. We also tested our OECTs after three months of storage in ambient atmosphere, and observed that both I D and g m remain unaffected ( Figure S9, Supporting Information), confirming a high operational stability of BBL-based OECTs.…”

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confidence: 99%

Complementary Logic Circuits Based on High‐Performance n‐Type Organic Electrochemical Transistors

et al. 2018

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Organic electrochemical transistors (OECTs) have attracted great attention as they hold significant promise for a variety of applications ranging from printable logic circuits for electronic textiles to drivers for sensors and flat panel display pixels, as well as to artificial synapse for neuromorphic computing. [1] Because of the low working bias, high sensitivity, and stability in aqueous environments, as well as biological and mechanical compatibility with live tissues, OECTs have also recently emerged as a technological solution to a variety of diagnostic and therapeutic applications. [2] A considerable amount of work has focused, for example, on approaches exploiting the principle of OECTs for the development of biomedical tools for chemical and biological sensing, [3] electrophysiological recording, [4] monitoring of cell viability, and barrier tissue integrity, [5] to name just a few. In an OECT, the electroactive polymer constituting the channel is in direct contact with an electrolyte and with the source and drain metal electrodes ( Figure 1A). Because of the soft and permeable nature of the electroactive polymers, ions are able to penetrate into the bulk of the transistor channel. [6] The operation of an OECT relies then on a reversible ion exchange and charge compensation process, which leads to a bulk doping of the organic conducting channel and to a modulation of the electronic conductivity between the source and drain contacts. Hence, OECTs transduce a modulation in the gate voltage (V G ) to a modulation in the drain current (I D ) running through the entire bulk of the channel. The figure-of-merit that quantifies the efficiency of this transduction is the transconductance, defined as g m = ∂I D /∂V G .The current state-of-the-art active material for OECTs is the mixed ion-electron conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). The volumetric doping and dedoping of PEDOT:PSS result in a modulation of the drain-source current of several orders of magnitude with a consequent high transconductance. [7] As PEDOT:PSS is doped in its pristine state, and thus highly conducting, the OECT operates in depletion mode. In addition, several polythiophene-based polymers have been reported as efficient electroactive channel materials for enhancement mode OECTs. [8] To date, however, essentially all reported OECTs have relied on hole transport (p-type), while the development of electron Organic electrochemical transistors (OECTs) have been the subject of intense research in recent years. To date, however, most of the reported OECTs rely entirely on p-type (hole transport) operation, while electron transporting (n-type) OECTs are rare. The combination of efficient and stable p-type and n-type OECTs would allow for the development of complementary circuits, dramatically advancing the sophistication of OECT-based technologies. Poor stability in air and aqueous electrolyte media, low electron mobility, and/or a lack of electrochemical reversibility, of available high-...

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Controlling the mode of operation of organic transistors through side-chain engineering

Cited by 394 publications

References 36 publications

Smaller Counter Cation for Higher Transconductance in Anionic Conjugated Polyelectrolytes

Smaller Counter Cation for Higher Transconductance in Anionic Conjugated Polyelectrolytes

Balancing Ionic and Electronic Conduction for High‐Performance Organic Electrochemical Transistors

Complementary Logic Circuits Based on High‐Performance n‐Type Organic Electrochemical Transistors

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