High Operation Frequency and Strain Tolerance of Fully Printed Oxide Thin Film Transistors and Circuits on PET Substrates

The major limitations of solution-processed oxide electronics include high process temperatures and the absence of necessary strain tolerance that would be essential for flexible electronic applications. Here, a combination of low temperature (<100 degrees C) curable indium oxide nanoparticle ink and a conductive silver nanoink, which are used to fabricate fully-printed narrow-channel thin film transistors (TFTs) on polyethylene terephthalate (PET) substrates, is proposed. The metal ink is printed onto the In2O3 nanoparticulate channel to narrow the effective channel lengths down to the thickness of the In2O3 layer and thereby obtain near-vertical transport across the semiconductor layer. The TFTs thus prepared show On/Off ratio approximate to 10(6) and simultaneous maximum current density of 172 mu A mu m(-1). Next, the depletion-load inverters fabricated on PET substrates demonstrate signal gain >200 and operation frequency >300 kHz at low operation voltage of V-DD = 2 V. In addition, the near-vertical transport across the semiconductor layer is found to be largely strain tolerant with insignificant change in the TFT and inverter performance observed under bending fatigue tests performed down to a bending radius of 1.5 mm, which translates to a strain value of 5%. The devices are also found to be robust against atmospheric exposure when remeasured after a month.

Automated summary

This study presents a method for low-temperature fabrication of oxide electronics using indium oxide nanoparticle ink and conductive silver nanoink on flexible PET substrates. The resulting printed thin-film transistors and inverters exhibit excellent performance and high tolerance to strain and atmospheric exposure.