Abstract:The molecular ordering of aqueous conducting polymers is controlled using a rational method. By introducing various ionic liquids, which have designed electrostatic interactions to PEDOT:PSS solutions, the evolution of the molecular ordering of the PEDOT is manipulated. Consequently, highly ordered nanostructures are achieved with a reduced π-π stacking distance of ≈3.38 Å and, thus, a maximum σ of ≈2100 S cm .
“…Figure b displays the conductivity of PEDOT:PSS films with different added amount of [EMIM][TCM]. In general, the PEDOT:PSS with [EMIM][TCM] composites exhibit substantially higher conductivities, which correlates well with previous studies where ionic liquids are showed to be good conductivity enhancers in conducting polymers . For instance, at 1.5 wt% [EMIM][TCM], the measured conductivity is around 1000 S cm −1 which is almost three orders of magnitude higher than that of the pristine PEDOT:PSS film (appropriate 1 S cm −1 ).…”
supporting
confidence: 81%
“…The current state‐of‐the‐art active conjugated polymer for OECTs is poly(3,4‐ethylenedioxythiophene) (PEDOT) which is commonly charge compensated by an immobile polymer anion, polystyrenesulphonate (PSS), Figure a . The pristine PEDOT:PSS thin films typically suffer from low electrical performance (conductivity: ≈1 S cm −1 ; hole mobility: 10 −3 cm 2 V −1 s −1 ), due to excessive insulating PSS content and lack of dense packing of PEDOT chains. One commonly used strategy is the addition of co‐solvent dispersion additive, ethylene glycol (EG), which leads to an increase in PEDOT aggregation or structural reorganization of the PEDOT domains into more continuous network and thus enhances the charge carrier mobility ( µ ) .…”
The use of organic electrochemical transistors (OECTs) for various applications ranging from neuromorphic devices [1] to transducers for biological sensing, including detection of ions, [2,3] metabolites (such as glucose [4,5] ), DNA, [6] antibodyantigen interaction, [7] and cancer cells [8] has received significant attention in recent years. An OECT consists of a conjugated polymer channel in direct contact with an electrolyte, where the operation involves doping and dedoping of the conjugated polymer by reversible exchange of ions present in an electrolyte under the application of a very low gate voltage (V G < 1 V). The measured drain current (I D ) of the polymer channel between the source and drain contacts is therefore modulated through accumulation or depletion of charges throughout the bulk of the polymer. The corresponding transconductance (g m = ∂I D /∂V G ) is typically large (up to 2.0 mS for micrometer-scale devices [9] ), making OECTs an efficient ionto-electron transducers, capable of amplifying small chemical signals and with high signal-to-noise ratios. One important advantage of OECTs is that they can be fabricated from biocompatible organic materials, enabling an amiable interface with cells and tissues in aqueous environments (water-based electrolytes). [10] Also, their simple structure allows the potential for large-area and low-cost electronics through their facile fabrication processes such as printing and easy integration with microfluidic lab-on-a-chip applications. [11,12] The OECT transconductance, g m , is defined as follows: [13] µ ( )where d, W, and L are the thickness, width, and length of the channel respectively, µ is the carrier mobility, C* is the volumetric capacitance, and V th is the threshold voltage of the channel. In particular, the µC* figure of merit dictates the carrier and ionic transport and therefore affects the g m parameter. [14] In general, a good OECT channel material needs to have good electronic transport properties (high µ) and allows effective ion penetration from the electrolyte into active channel (high C*). The ability to have mixed ionic and electronic Organic electrochemical transistors (OECTs) are highly attractive for applications ranging from circuit elements and neuromorphic devices to transducers for biological sensing, and the archetypal channel material is poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), PEDOT:PSS. The operation of OECTs involves the doping and dedoping of a conjugated polymer due to ion intercalation under the application of a gate voltage. However, the challenge is the trade-off in morphology for mixed conduction since good electronic charge transport requires a high degree of ordering among PEDOT chains, while efficient ion uptake and volumetric doping necessitates open and loose packing of the polymer chains. Ionic-liquid-doped PEDOT:PSS that overcomes this limitation is demonstrated. Ionic-liquid-doped OECTs show high transconductance, fast transient response, and high device stability over 3600 switching cycles. The ...
“…Figure b displays the conductivity of PEDOT:PSS films with different added amount of [EMIM][TCM]. In general, the PEDOT:PSS with [EMIM][TCM] composites exhibit substantially higher conductivities, which correlates well with previous studies where ionic liquids are showed to be good conductivity enhancers in conducting polymers . For instance, at 1.5 wt% [EMIM][TCM], the measured conductivity is around 1000 S cm −1 which is almost three orders of magnitude higher than that of the pristine PEDOT:PSS film (appropriate 1 S cm −1 ).…”
supporting
confidence: 81%
“…The current state‐of‐the‐art active conjugated polymer for OECTs is poly(3,4‐ethylenedioxythiophene) (PEDOT) which is commonly charge compensated by an immobile polymer anion, polystyrenesulphonate (PSS), Figure a . The pristine PEDOT:PSS thin films typically suffer from low electrical performance (conductivity: ≈1 S cm −1 ; hole mobility: 10 −3 cm 2 V −1 s −1 ), due to excessive insulating PSS content and lack of dense packing of PEDOT chains. One commonly used strategy is the addition of co‐solvent dispersion additive, ethylene glycol (EG), which leads to an increase in PEDOT aggregation or structural reorganization of the PEDOT domains into more continuous network and thus enhances the charge carrier mobility ( µ ) .…”
The use of organic electrochemical transistors (OECTs) for various applications ranging from neuromorphic devices [1] to transducers for biological sensing, including detection of ions, [2,3] metabolites (such as glucose [4,5] ), DNA, [6] antibodyantigen interaction, [7] and cancer cells [8] has received significant attention in recent years. An OECT consists of a conjugated polymer channel in direct contact with an electrolyte, where the operation involves doping and dedoping of the conjugated polymer by reversible exchange of ions present in an electrolyte under the application of a very low gate voltage (V G < 1 V). The measured drain current (I D ) of the polymer channel between the source and drain contacts is therefore modulated through accumulation or depletion of charges throughout the bulk of the polymer. The corresponding transconductance (g m = ∂I D /∂V G ) is typically large (up to 2.0 mS for micrometer-scale devices [9] ), making OECTs an efficient ionto-electron transducers, capable of amplifying small chemical signals and with high signal-to-noise ratios. One important advantage of OECTs is that they can be fabricated from biocompatible organic materials, enabling an amiable interface with cells and tissues in aqueous environments (water-based electrolytes). [10] Also, their simple structure allows the potential for large-area and low-cost electronics through their facile fabrication processes such as printing and easy integration with microfluidic lab-on-a-chip applications. [11,12] The OECT transconductance, g m , is defined as follows: [13] µ ( )where d, W, and L are the thickness, width, and length of the channel respectively, µ is the carrier mobility, C* is the volumetric capacitance, and V th is the threshold voltage of the channel. In particular, the µC* figure of merit dictates the carrier and ionic transport and therefore affects the g m parameter. [14] In general, a good OECT channel material needs to have good electronic transport properties (high µ) and allows effective ion penetration from the electrolyte into active channel (high C*). The ability to have mixed ionic and electronic Organic electrochemical transistors (OECTs) are highly attractive for applications ranging from circuit elements and neuromorphic devices to transducers for biological sensing, and the archetypal channel material is poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate), PEDOT:PSS. The operation of OECTs involves the doping and dedoping of a conjugated polymer due to ion intercalation under the application of a gate voltage. However, the challenge is the trade-off in morphology for mixed conduction since good electronic charge transport requires a high degree of ordering among PEDOT chains, while efficient ion uptake and volumetric doping necessitates open and loose packing of the polymer chains. Ionic-liquid-doped PEDOT:PSS that overcomes this limitation is demonstrated. Ionic-liquid-doped OECTs show high transconductance, fast transient response, and high device stability over 3600 switching cycles. The ...
“…Graphene and CNTs suffer from high sheet resistance due to low intrinsic carrier concentration and high contact resistance, respectively . PEDOT:PSS shows high sheet resistance as well because of its low inherent electrical conductivity (σ dc ≈ 10 0 S cm −1 ) . Among the aforementioned materials, silver nanowire (AgNW) transparent electrodes underscore the potential to replace ITO, because they provide a tradeoff between conductivity and transparency, flexibility, and solution processability.…”
The continuous, large-area solution-processed production of silver nanowire (AgNW) transparent conducting films with outstanding optoelectronic and mechanical performance remains a challenge. Here, efficient welding of AgNWs is demonstrated using ultraviolet A (UVA) with the specific wavelength range from ≈320 to ≈400 nm based on a nanoscale photothermal process. The AgNW welding shows a self-terminating and self-limiting nature, and sensitivity to diameter of AgNWs. Sheet resistance of the UVA-illuminated (UVAI) AgNW films rapidly drops within 2 min without loss of transmittance. For the UVAI AgNW (30 nm in diameter) film, decrement of sheet resistance approaches three orders of magnitude (≈10 5 -10 2 Ohm sq −1 ) with original transmittance being (97%) retained, which significantly enhances its optoelectronic properties. Enhanced mechanical flexibility, electromagnetic interference (EMI) shielding effectiveness (SE), and heating performance are obtained in the UVAI AgNW films. The SE and plateau temperature of the AgNW film increase to 25 dB and 50 °C after illumination, respectively. Smart window, transparent heater, and triboelectric nanogenerator based on the UVAI AgNW film demonstrate its versatile applications in optoelectronics. Finally, the welding method is easily integrated into a roll-to-roll process to manufacture AgNW film with a low sheet resistance of 25 Ohm sq −1 and a high transmittance of 90%, and excellent flexibility.
“…Overall, we had expected Au vapor deposition to give low contact resistance but it turns out to be a poor match with the important factors for the legs’ performance optimizations, such as having DMSO addition to PEDOT:PSS and the ball-milled TTF-TCNQ without PVC. This result suggests that we need to explore non-volatile additives to PEDOT:PSS [18] and polymer-based n-type materials soluble to common solvents [19]. 10.1080/14686996.2018.1487239-F0008Figure 8.Schematic of the Au penetrated π-type TE module.…”
To examine the potential of organic thermoelectrics (TEs) for energy harvesting, we fabricated an organic TE module to achieve 250 mV in the open-circuit voltage which is sufficient to drive a commercially available booster circuit designed for energy harvesting usage. We chose the π-type module structure to maintain the temperature differences in organic TE legs, and then optimized the p- and n-type TE materials’ properties. After injecting the p- and n-type TE materials into photolithographic mold, we eventually achieved 250 mV in the open-circuit voltage by a method to form the upper electrodes. However, we faced a difficulty to reduce the contact resistance in this material system. We conclude that TE materials must be inversely designed from the viewpoints of the expected module structures and mass-production processes, especially for the purpose of energy harvesting.
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