Correlation of on-state conductance with referenced electrochemical potential in ion gel gated polymer transistors

Abstract

We report direct measurement of the electrochemical potential at organic semiconductor/gate dielectric interfaces in printed polymer transistors employing a gel electrolyte as the gate insulator. An oxidized silver wire reference electrode was embedded into the gel electrolyte, and its potential relative to the grounded source contact was measured simultaneously with the transistor transfer characteristics. The referenced turn-on voltages of transistors based on three common polymer semiconductors [(poly-3-hexylthiophene, poly(3,3‴-didodecylquaterthiophene), and poly(9,9′-dioctylfluorene-co-bithiophene)] were found to correlate with the reported highest occupied molecular orbital levels (ionization potentials) for these materials. Further, analysis of the transfer characteristics revealed a negative differential transconductance regime at high gate-induced carrier densities (∼1015 cm−2), which we attribute to a combination of band filling and a mobility lowering effect.

Large-scale organic nanowire lithography and electronics

“…The m FET calculated from gatedisplacement current gave more reasonable values (average m FET : B3.8 cm 2 V À 1 s À 1 ) than that calculated from equation (3). Although the induced carrier density is inversely proportional to m FET , the calculated m FET is much higher than those of general P3HT FET devices (Supplementary Table S1), because the large induced hole density fills the trap of the P3HT channel and smoothes the electrostatic potential variation that occurs in the channel due to trapped charges 29 . In addition, we found that the core-shell structure of P3HT:PEO-blend NWs and extended chain orientation of P3HT along the wire axis contributed to the high m FET of ion-gel-gated NW FETs (Supplementary Figs S6-S8, S15 and S16, and Supplementary Notes S7 and S8).…”

“…Instead of thin-film FET model, m FET can be computed using gate-displacement current and induced carrier density (P i ), 28,29 …”

“…To calculate m FET in ion-gel-gated NW FETs, we used two different equations: the conventional thin-film FET equation 21,23 and the equation based on the gate-displacement current and induced charge density 28,29 . First, m FET was calculated from the simple 'thin-film FET model' (equation 3) 21,23 .…”

High performance photolithographically-patterned polymer thin-film transistors gated with an ionic liquid/poly(ionic liquid) blend ion gel

“…These can be particularly prominent in electrolyte-gated OTFTs, due to sluggish ionic diffusion effects. 27 As represented in figure 1.a, the devices were fabricated in air on a glass substrate and bottom Au source and drain electrodes were defined by photolithography, forming a channel of width W = 2000 µm and length L = 10 µm, resulting in a reasonably large W/L ratio of 200. P3HT was then spin-coated at 2000 rpm from a 5 mg mL −1 solution in 1,2-dichlorobenzene in order to form thin-films of thickness ≈ 20 nm.…”

Electric-Field-Induced Superconductivity on an Organic/Oxide Interface

“…A Ag/AgO electrode was fabricated by oxidizing a Ag wire with a diameter of 50 m by immersing in piranha solution (H 2 SO 4 /H 2 O 2 , 7 : 3) for 1 min. 29) The gate bias was repeatedly swept from À8 to 8 V with a rate of 3 mV/s at 300 K, and we simultaneously obtained a leakage current between the channel and the gate and sheet conductance of the channel by the four-terminal method. Figures 4(a) and 4(b) show the leakage current density and sheet conductance as a function of gate bias and potential of the reference electrode.…”