||Conductive metallic features that are flexible could have applications in integrated circuits, ranging from large-area electronics to low-end applications. Here, we show the creation of conductive silver thin film and wire on the transparent flexible polyethylene terephthalate (PET) substrate by a room-temperature chemical reduction process. One-step synthesis and spectroscopic characterizations of size-controlled silver nanoparticles are also described. Transmission electron microscopy, FT-IR, thermal gravimetric-mass analysis, X-ray photoelectron spectroscopy and synchrotron radiation x-ray diffraction were used to characterize the dodecanoate-protected silver nanoparticles. Silver metal film and wire were produced by soaking the dodecanoate-protected silver nanoparticle film and wire that were prepared, respectively, by spin-coating and by directly drawing with a commercial Epson T50 inkjet printer onto the flexible PET substrate using Ag nanoparticles suspended in cyclohexane (10 % by weight) as the ink in an aqueous solution containing 80% N2H4. The resistivities of our Ag films are actually lower when they are compared to the Ag thin films prepared by other conventional chemical routes, such as using silver salts as metallo-organic precursors. We suggest that the advantage of using nanoparticles as precursor may be an explanation for the lower resistivity.|
The novelty of this study is laboratory formulation of silver ink adapted for inkjet printing of conductive metallic features on the flexible polyimids (PI) substrate that could have applications in integrated circuits, ranging from large-area electronics to low-end applications. New silver precursor for printing conductive patterns with empirical formula of [Ag(dien)](tmhd), where tmhd = 2,2,6,6-tetramethyl-3,5-heptane-
dionato and dien = diethylenetriamine, was synthesized by a simple and environmental friendly method. The viscosity and surface tension of the organic solvent system were adequately adjusted by adding ethyl cellulose and hexylamine, yielding a high wt% Ag ink that is suitable for inkjet printing. Silver patterns were produced by the thermal annealing of freshly prepared silver features that were prepared, respectively, by spin-coating and by directly drawing with a piezoelectric inkjet printer onto the flexible PI substrate using silver precursor (60 wt%) dissolved in hexylamine (39 wt%) and ethyl cellulose (1 wt%) with viscosity of 9-11 mPa s in air at 150-250 C. The silver patterns were characterized by means of scanning electron microscopy, FT-IR, thermal gravimetric-mass analysis, X-ray photoelectron spectroscopy and synchrotron radiation x-ray diffraction. The resistivities of our silver patterns are actually lower when they are compared to those prepared by other research groups, such as using water-based silver salts as inks. We suggest that the advantage of the high wt% silver ink in organic
solvent based system may be an explanation for the lower resistivity.