Tuning Threshold Voltage of Electrolyte-Gated Transistors by Binary Ion Doping

Abstract

Electrolyte-gated transistors (EGTs) operating at low voltages have attracted significant attention in widespread applications, including neuromorphic devices, nonvolatile memories, chemical/biosensors, and printed electronics. To increase the practicality of the EGTs in electronic circuits, systematic control of threshold voltage (V th ), which determines the power consumption and noise margin of the circuits, is essential. In this study, we present a simple strategy for systematically tuning V th to almost half of the operating potential range of the EGT by controlling the electrochemical doping of electrolyte ions into organic p-type semiconductors. The type of anion in the ionogel determines V th as well as other transistor characteristics, such as the subthreshold swing and mobility, because the positive hole carriers are the majority carriers. More importantly, V th can be finely controlled by binary anion doping using ionogels with two anions with varying molar fractions at a fixed cation. In addition, the binary anion doping successfully controls the inversion characteristics of ion-gated inverters. As unlimited combinations of ion pairs are possible for ionogels, this study opens a route for controlling the device characteristics to expand the practicality and applicability of ionogel-based EGTs for next-generation ionic/electronic devices.

Relation between Polymer Semiconductor Morphology and the Ion-Doping Effect in Electrolyte-Gated Transistors

“…Ion-doping effect into P3HT in EGTs can be identified by in situ UV–vis absorbance spectra measurement as a function of applied gate bias (Figure ). When the ions penetrate the P3HT film, the material undergoes chemical oxidation, leading to an absorption spectrum at 505 nm . For CF-P3HT, the sample shows a strong absorption with the applied gate bias.…”

“…When the ions penetrate the P3HT film, the material undergoes chemical oxidation, leading to an absorption spectrum at 505 nm. 28 For CF-P3HT, the sample shows a strong absorption with the applied gate bias. In the case of CB-and DCB-P3HTs, however, the absorption intensity was drastically reduced.…”

Tuning Gate Potential Profiles and Current–Voltage Characteristics of Polymer Electrolyte-Gated Transistors by Capacitance Engineering

“…A variety of different gate electrode architectures are used for polymer EGTs. − ,− In fact, one of attractive features of EGTs is that the gate electrode can be offset from the source-drain channel, which makes fabrication easier in some instances, albeit with a loss in switching speed. − ,,− , Gate electrode materials include metals such as Au, conducting polymers such as PEDOT:PSS as in Figure , and conducting porous carbon, for example. ,,− Often times, not much attention is paid to the size of the contact area between the gate and the electrolyte, despite a few previous studies indicating that the gate electrode significantly influences charge accumulation and EGT performance. − Here, we show that changing the gate–electrolyte contact area, which changes its interfacial capacitance, can have a profound impact on the measured current–voltage characteristics of EGTs. In fact, undersizing the gate electrode leads to large potential drops at the gate–electrolyte interface and produces drain current-gate voltage ( I D – V G ) curves that saturate at large V G ; it also causes large I D – V G hysteresis.…”

Modulation of polyaniline memristive device switching voltage by nucleotide-free analogue of vitamin B12

“…While the switching times of organic neuromorphic devices can be controlled through changes in geometry and morphology of the devices active area [27], their switching voltage must be fine-tuned for a specific task to ensure compatibility with an existing system. This can be achieved through different approaches, such as altering the ionic species of the electrolyte solution in electrochemically switching devices [35], modifying the gate with various organic molecules [36] and even introducing bacteria to the active region to shift the switching potential through enzymatic activity [37]. To date, the possibility of modulating of the switching potential of PANI thin films within 50 mV range by changing electrolyte anions has been demonstrated [38,39].…”