Overcoming Electrochemical Instabilities of Printed Silver Electrodes in All-Printed Ion Gel Gated Carbon Nanotube Thin-Film Transistors

Malo Robin; Luis Portilla; Miaomiao Wei; Tianqi Gao; Jianwen Zhao; Shuangshuang Shao; Vincenzo Pecunia; Zheng Cui

doi:10.1021/acsami.9b14916

Overcoming Electrochemical Instabilities of Printed Silver Electrodes in All-Printed Ion Gel Gated Carbon Nanotube Thin-Film Transistors

ACS Appl Mater Interfaces. 2019 Nov 6;11(44):41531-41543. doi: 10.1021/acsami.9b14916. Epub 2019 Oct 22.

Authors

Malo Robin¹, Luis Portilla^{1

2}, Miaomiao Wei¹, Tianqi Gao¹, Jianwen Zhao¹, Shuangshuang Shao¹, Vincenzo Pecunia², Zheng Cui¹

Affiliations

¹ Printable Electronics Research Centre, Suzhou Institute of Nanotech and Nano-Bionics , Chinese Academy of Sciences , No. 398 Ruoshui Road, SEID, Suzhou Industrial Park , Suzhou , Jiangsu Province 215123 , PR China.
² Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Joint International Research Laboratory of Carbon-Based Functional Materials and Devices , Soochow University , 199 Ren'ai Road , Suzhou , Jiangsu 215123 , PR China.

PMID: 31597420
DOI: 10.1021/acsami.9b14916

Abstract

Silver ink is the most widely used conductive material for printing electrodes in the fabrication of all-printed ion gel gated transistors because of their high conductivity and low cost. However, electrochemical instability of printed silver electrodes is generally one of the biggest issues, whether it is in air where silver gets oxidized or in a moisture environment where electrochemical migration occurs. Notwithstanding, the electrochemical stability of printed silver electrodes in ion gel medium has not been studied so far. In this work, we studied the electrochemical instabilities of printed silver electrodes in fully printed ion gel gated single-walled carbon nanotube (SWCNT) thin-film transistors (TFTs) and developed some strategies to overcome these issues. All-printed ion gel-based p-type SWCNT TFTs were employed to investigate the impact of electrochemical instabilities on the electrical behavior of printed SWCNT TFTs. The results have demonstrated that printed silver was unstable at anodic and cathodic polarization because of the corrosion by the ionic liquid. Besides, anodic corrosion of silver source/drain electrodes was shown to be responsible for the electrical failure of printed SWCNT TFTs in both the linear and saturated regime. These issues were completely resolved when preventing printed silver electrodes from coming into direct contact with ion gels. For example, ion gels were partially printed in device channels to avoid contacting the printed silver source and drain electrodes. At the same time, silver side-gate electrodes were replaced by inkjet-printed PEDOT:PSS electrodes to avoid gate electrode-related instabilities. Consequently, all-printed electrochemically stable SWCNT TFTs fabricated were obtained with enhanced performance of higher I_ON/I_OFF ratios (10⁵ to 10⁶), smaller subthreshold slopes (∼70 mV/dec), and smaller hysteresis (ΔV = 0.025 V) at gate voltages from 1.2 to -0.5 V. Additionally, the polarity of all-printed SWCNT TFTs was converted from the p-channel to ambipolar while achieving lower leakage currents.

Keywords: all-printed transistors; ambipolar transistors; carbon nanotube thin film transistors; electrochemical stability; ion gel; printed silver corrosion; printed silver electrodes.