Reactive Silver Oxalate Ink Composition with Enhanced Curing Conditions for Flexible Substrates

Abstract

A solid silver-ligand complex, μ-oxolato-bis(ethylenediaminesilver(I)), was developed for formulating particle-free conductive metal-organic decomposition (MOD) inkjet inks. The complex comprises both a high molar silver content and solubility in inkjet compatible polar solvents. An aqueous ink formulation with 29.5 wt % silver content was developed and inkjet printed onto glass, polyethylene terephthalate, and polyimide substrates. A new hybrid thermal-photonic curing approach resulting in substantially improved electrical properties and substrate adhesion is presented. Silver conductive traces were measured to have bulk resistivity of 4.26 × 10 Ω m, which is 2.7 times that of bulk silver. One-pot complex synthesis yielded an easily isolated, and stable, solid product that can be formulated when needed thereby improving shelf life.

Metal particle-free inks for printed flexible electronics

“…One approach is to use ligands possessing multiple silver binding sites. 99 Amines, cyanides, and thiocyanate have been considered since they can solubilize and stabilize the silver precursors in alcohol-based solvents and can increase the susceptibility of silver ion to reduction. 73 However, considering the toxicity and environmental implication, amines are the main choices.…”

“…18), Zope et al also formulated a particle-free ink with 25.9% silver content for inkjet printing. 99 A hybrid heat-photonic curing method was employed to improve the electrical properties and adhesion of the ink. Silver conductive traces showed a resistivity of 4.26 mO cm, which is 2.7 times that of bulk silver.…”

“…As described in Section 3, copper or silver particle-free inks have been developed due to their low cost, flexibility in preparation and a relatively low-temperature sintering in comparison with the nano silver or copper-based inks. The ink of copper formate 52,88,92,101,103,108,132,133 or silver oxalate 51,99,106 has made significant development with their advantages over other types of metal inks. This type of ink, however, also has drawbacks.…”

Research Status and Prospects of Particle-Free Silver Conductive Ink

“…The pattern resistivity printed on a 150° C. cured PI substrate is only 8.6×10 −6 Ω.cm with good adhesion. In view of the low stability of the ink, which cannot be stored for a long time, Zope [23] developed a solid ink. Using silver oxalate as a precursor and ethylenediamine as a complexing agent, a solid complex can be obtained.…”

One-pot synthesis of a stable and cost-effective silver particle-free ink for inkjet-printed flexible electronics

“…Conductive inks play a central role for printed flexible electronics since they find application in a wide range of newly-emerged electronic and energy devices. 3,4 Currently, a number of inks based on silver, [5][6][7][8][9] copper, [10][11][12][13][14][15][16] graphene, [17][18][19][20][21] carbon 22,23 and conductive polymers, [24][25][26] have been explored for printed flexible electronics. Among them, silver-based inks have been the favored metal inks because they are more costeffective than Au-based metal inks, more stable than Cu-based on inks and have better conductivity than polymer or carbonbased inks.…”