Inkjet-printable and low-temperature curable Ag–Ag2O mixed-phase conductive nanoink for flexible electronic applications.

Printed and flexible electronics is rapidly developing to cater the large demands of wearable and consumer electronic needs. However, among the wide variety of printed electronic and energy storage/energy conversion devices, only conductive inks, sensors and light-emitting diodes (LEDs) have achieved commercial success. Notably, the printable conducting inks are not only essential for the passive components in electronic devices; their widespread use covers electrical interconnects, transparent touch sensors, heaters, antistatic coating, antenna etc. Further to ascertain flexibility and commercial relevance, it is important to be able to print devices onto inexpensive substrates; the most preferred choice of substrates would, therefore, be paper or polyethylene terephthalate (PET), which are widely used in consumer products and in packaging industries. However, this requires stringent process temperature control (≤ 120 °C). Worldwide extensive research on inkjet printable conductive silver inks has resulted in large variety of inks, nevertheless, there are not many choices for such low-temperature curing conditions. Here we demonstrate a precisely controlled synthesis of a polymer ligand stabilized mixed-phase Ag–Ag₂O nanoparticles, where each individual particle has a protective shell, hence, offering an excellent shelf life. Furthermore, the synthesised nanoink in a suitable solvent allows the Ag₂O phase to convert to silver at a temperature as low as 80 °C. Meanwhile, the large volume change associated with the Ag₂O to Ag conversion ensures removal of the stabilizing ligands from the particle surface and offers resistivity of 4.5 × 10^–4 Ω cm and 3.3 × 10^–5 Ω cm, when annealed at 80 °C and 120 °C, respectively. In this work, the Ag₂O–Ag mixed-phase nanoink has been inkjet-printed onto standard photo-paper and typical bending-fatigue tests have demonstrated excellent strain tolerance up to 4% and for 10⁴ cycles. [ABSTRACT FROM AUTHOR]