Patterning of High-Viscosity Silver Paste by an Electrohydrodynamic-Jet Printer for Use in TFT Applications

Area of Science:

• Materials Science
• Nanotechnology
• Electrical Engineering

Background:

• Conventional inkjet printing faces limitations with high-viscosity materials.
• Electrohydrodynamic (EHD) jet printing offers superior resolution and material compatibility.
• Silver nanoparticle (Ag NP) pastes are crucial for printed electronics.

Purpose of the Study:

• To investigate the formulation of high-viscosity Ag NP pastes for EHD jet printing.
• To achieve high-resolution printed patterns with low sheet resistance.
• To fabricate solution-processed oxide thin-film transistors (TFTs) using EHD-printed Ag electrodes.

Main Methods:

• Formulation of Ag NP pastes (4000 cPs) with additives for EHD jet printing.
• EHD jet printing of Ag NP pastes to create fine patterns.
• Fabrication and electrical characterization of oxide TFTs with EHD-printed Ag electrodes.

Main Results:

• Achieved printable Ag NP pastes with additives, enabling pattern lines narrower than 100 μm.
• Obtained an average sheet resistance of 0.027 Ω □⁻¹ for printed Ag lines.
• Successfully fabricated solution-processed oxide TFTs with EHD-printed Ag electrodes for the first time.
• The fabricated TFTs exhibited a high current ratio (1.5 × 10⁶), mobility (~1 cm² V⁻¹ s⁻¹), threshold voltage (21.5 V), and subthreshold slope (3.05 V dec⁻¹).

Conclusions:

• EHD jet printing is a viable technique for high-resolution patterning of high-viscosity Ag NP pastes.
• The developed Ag NP paste formulation and EHD printing process are suitable for fabricating functional electronic devices.
• This work demonstrates the potential of EHD jet printing for advanced printed electronics, including oxide TFTs.