A Universal Platform for Fabricating Organic Electrochemical Devices

Abstract

cost-effectively processed at room temperature, and to volumetrically uptake large amounts of electrolytes, OEDs have recently garnered much interest for applications in bioelectronics. [1][2][3] These include biosensing, energy storage, neural recording, and stimulation, [4,5] drug delivery, [6] and electroceuticals [7] to name a few. Out of the many available architectures, a device of choice that has been heavily investigated in recent years is the organic electrochemical transistor (OECT). In a typical OECT device, the conductivity of a polymer channel, which is probed by a set of source and drain electrodes, is actively controlled by varying the voltage applied between the channel and a third gate electrode both of which reside in the same electrolyte solution. The choice for gate materials, channel materials, electrolyte solutions, and device dimensions can all be designed to obtain desired device characteristics. Thin photolithographically defined devices, for instance, are favored for high speed (>1 kHz) operation whereas large devices with thick polymer channels are more often chosen for their high transconductance. [8][9][10] In general, OECTs operate at relatively low voltages (<1 V) that are suitable for aqueous environments and biological tissues, and have been successfully used to monitor the integrity of barrier tissues, [11,12] in vitro glucose concentrations [13,14] and in vivo neural activities. [15] In OECTs, ions penetrate the whole polymer film, as facilitated by the swelling processes induced by the solvent. While such process is not strictly necessary, as ionic liquids have been shown to also induce transistor-like behavior in conjugated polymers, [16,17] compared to ionic liquid-gated devices, OECTs provide the opportunity to decouple ionic transport, through swelling caused by the electrolyte solvent, from the ability of the ions to generate mobile charges in the polymer.Despite recent advances in device fabrication and materials development, however, only a select few polymers have been found to stably operate as active OECT channels in aqueous environments. Current state-of-the-art OECTs are fabricated using the highly conductive mixture of poly(3,4ethylenedioythiophene) doped with poly(styrene sulphonate) (PEDOT:PSS). [8] While this materials blend exhibits high transconductance and good stability, the details of the chemical composition are often unknown due to the proprietary nature A general method and accompanying guidelines for fabricating both nonaqueous and aqueous based organic electrochemical devices (OECTs) using water-insoluble hydrophobic semiconducting polymers are presented. By taking advantage of the interactions of semiconducting polymers in certain organic solvents and the formation of a stable liquid-liquid interface between such solvents and water, OECTs with high transconductance, ON/OFF ratios of up to 10 6 , and enhancements in stability are successfully fabricated. Additionally, key fundamental properties are extracted of both the device and the active channel ma...

Enhanced Charge Injection Properties of Organic Field‐Effect Transistor by Molecular Implantation Doping

“…As a result, the position of the gate dielectrics was normally restricted to the top side of devices (i.e., FETs in a top‐gate structure) in order to enhance the charge injection from metal electrodes to the accumulation layer formed on the top surface of the polymer . Recently, the combination of poly(2,5‐bis(3‐tetradecylthiophen‐2‐yl)thieno[3,2‐b]thiophene) (PBTTT) and 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F 4 ‐TCNQ) as host and dopant material, respectively, has produced a highly conducting polymer that has been studied as a candidate for a synthetic metal and high power‐factor thermoelectric material . Interestingly, this combination achieved an efficient bulk‐doping of PBTTT by solid‐state diffusion which implied that the F 4 ‐TCNQ dopant molecules diffused into the PBTTT film all the way down to the interface between the PBTTT film and the SiO 2 /Si substrate .…”

Biomimetic Electronic Devices for Measuring Bacterial Membrane Disruption

“…Indeed, surface plasmon resonance studies using chips functionalized with either lipid MLs or bilayers have found little difference in terms of binding of antimicrobial compounds, indicating that for the initial interactions, the inner leaflet of the membrane is not essential . We chose to use poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) as the active material of our lipid ML‐integrated transducer, following studies showing P3HT allows ion penetration upon swelling in an organic solvent, enabling the so‐called OECT mode of operation. The electrolyte solution was made by dissolving an anhydrous tetrabutylammonium hexafluorophosphate (TBA‐PF 6 ) ion pair in dichloromethane (DCM), found to have optimal characteristics in terms of solubility, as well as ion exchange properties between the polymer and the electrolyte.…”

Organic semiconductors for biological sensing

“…Faria and coworkers recently showed how several hydrophobic polymers, taken directly from the organic electronics community without laborious side-chain modifications, could display mixed conduction when interfaced with a non-aqueous liquid. 139 Work by Ginger and co-workers have likewise helped shed light on ion conduction in archetypical P3HT-based OECTs, which is highly dependent on the size of the ions and their hydration shells. 197 Such multi-faceted approaches and inter-disciplinary collaborations across (bio)chemistry, physics and engineering are crucial for rapid development of new materials, device architectures and sensing platforms.…”

“…20 A 2018 work by Pitsalidis et al therefore selected P3HT as a suitable material for an OECT, 37 their reasoning citing its known ability to facilitate ion penetration by swelling in organic solvents. 139,140 Their P3HTbased OECT was able to measure modelled bacterial membrane disruption by application of antibiotics. The device featured a top-gate electrode exposed to an aqueous phase, with a dichloromethane phase below containing the electrolyte tetrabutylammonium hexafluorophosphate (TBA-PF6) in contact with the semiconducting material.…”