Solid-State Organic Electrolyte-Gated Transistors Based on Doping-Controlled Polymer Composites with a Confined Two-Dimensional Channel in Dry Conditions

Abstract

We report comprehensive and comparative studies on chemical and electrochemical controls of doping characteristics of various poly­(3,4-ethylenedioxythiophene) (PEDOT) composites complexed with sulfonates. Chemical treatment of PEDOT composites was conducted with a dedoping agent, tetrakis­(dimethylamino)­ethylene (TDAE), resulting in the changes in conformation and bulk charge-carrier density. Electrochemical control of doping states was done with a solid-state ionogel based on an ionic liquid dispersed in a polymer matrix. With this approach, we can fabricate solid-state organic electrolyte-gated transistors (OEGTs) with a large current modulation, a high mobility of holes, and a low driving voltage. Our OEGTs are operational in a dry environment and, surprisingly, form the two-dimensional channel of the interfacial charge carriers modulating the conductance under gate bias, unlike conventional liquid-based OEGTs. The charge-carrier mobility and the on-to-off current ratio reach up to ∼7 cm2 V–1 s–1 and over 104, respectively, from the chemically dedoped PEDOT composites. The ionogel-based gating of the layer of TDAE-treated PEDOT composites induces a reversible transition between a highly doped bipolaronic state and neutral/polaronic states, as revealed by the absorption profiles under gate bias. We also demonstrate in-plane OEGTs, in which the dedoped channel and the conductive source/drain electrodes are made of a single PEDOT composite layer.

Sigmoidal Dependence of Electrical Conductivity of Thin PEDOT:PSS Films on Concentration of Linear Glycols as a Processing Additive

“…Figure 1a shows that the sheet resistances of the PEDOT:PSS films depend on the processing conditions. The sheet resistance of the films was clearly reduced when linear glycols were added, which also agrees to the previous studies (See Table S1) [4,22,28,[32][33][34][39][40][41]. Even at a low concentration of 0.1 M of TEG, the sheet resistances dropped to 565 Ω/sq and eventually stabilized at higher concentrations.…”

“…We investigated the optical properties of PEDOT:PSS films using UV-Vis-NIR spectrophotometer, since transmittance is a critical factor for applications in transparent electrodes and the spectra can also provide information on the doping states of the PEDOT composites (Figure 2) [3,8,22,46,47]. Transmittance (T) spectra of the PEDOT:PSS films made from dispersions with the additives (1 M), regardless of the structural variations, showed a fairly high optical transparency of T > 90% in the visible region with a peak value at around 450 nm.…”

“…The high conductivity and easy control of doping states have enabled its use as a promising p-type thermoelectric material [15][16][17][18][19]. Through electrochemical doping and dedoping, it is also possible to use PEDOT composites as a conductance-controllable layer in transistor [20][21][22]. Bioelectronic applications have also been sought from the PEDOT composites [23,24].…”

Electrical Tuning of Plasmonic Conducting Polymer Nanoantennas

“…We here utilize that the redox state of conducting polymers can be modulated electrochemically. [ 39–43 ] Figure a shows the basic device structure, based on PEDOT:Sulf nanodisks on an ITO/glass substrate, coated by an ion gel followed by a second ITO/glass substrate. The two ITO layers act as electrodes and are separated by the ion gel containing the ionic liquid 1‐ethyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM + ][TFSI − ]) in a mixture of the copolymer poly[(vinylidene fluoride)‐ co ‐hexafluoropropylene] (PVDF‐HFP) in acetone.…”

“…The small undulations are attributed to optical interference in the thin‐film device structure due to the sandwiched ion gel, as also observed without the nanodisks (Figure S12a, Supporting Information) and previously reported for similar ion gel components and device structures as used in this work. [ 43 ] d) Normalized extinction at the plasmonic peak position of around 1800 nm over time during multiple (50) switching cycles, with the inset showing results for the 1st and 41st cycles.…”