Date on Master's Thesis/Doctoral Dissertation

12-2016

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Chemical Engineering

Degree Program

Chemical Engineering, PhD

Committee Chair

Druffel, Thad

Committee Co-Chair (if applicable)

Sunkara, Mahendra

Committee Member

Starr, Thomas

Committee Member

Walsh, Kevin

Committee Member

Willing, Gerold

Author's Keywords

conductive inks; conductive films; intense pulsed light; copper; graphene oxide

Abstract

This research focuses on the investigation of Earth abundant copper and carbon based nanomaterials that are subjected to Intense Pulsed Light Processing to create conductive films, as future flexible electronics and renewable energy solutions would benefit from the quick and scalable production of conductive films. Use of nanomaterials in their oxide/hydroxide forms leads to higher stability in aqueous inks for efficient large area solution deposition. IPL Processing utilized 2044 μs pulses ranging from 589 J - 2070 J over an area of 1.9 cm x 30.5 cm, with energy densities of 10.1, 12.8, 15.8, 19.2, 22.9, 26.8, 31.1 and 35.7 Jcm-2, of non-coherent white light in wavelengths ranging from UV to NIR (240 nm – 1,000 nm) through a xenon lamp. The rapid pulses induce localized temperature increases in the films, flexible plastic substrates can be used without degradation. Three different morphological systems and nanomaterials were studied: 1D (copper hydroxide nanowires), 2D (Graphene Oxide nanosheets), and 3D (cuprous oxide encapsulated by nickel oxide nanoparticles & also copper nitrate hydroxide nanoparticles). The nanomaterials were rapidly reduced into conductive films via Intense Pulsed Light Processing aided through the organic decomposition of additives, providing a reducing environment. Through inclusion of different materials and morphologies, nanoscale manipulations can lead to breakthroughs in advanced materials and additive manufacturing. Cu2O (20nm) nanoparticles encapsulated with a NiO layer were synthesized to explore protecting the Cu from oxidation and diffusion into Si based photovoltaic applications. The room temperature synthesis and IPL processes easily prevented formation of alloys at the copper-nickel interface. The encapsulation was shown to reduce Cu diffusion into Si. Copper nitrate hydroxide, Cu2(OH)3NO3, was synthesized under ambient conditions with copper nitrate and potassium hydroxide reagents and processed by IPL. Films were deposited by screen-printing and then subjected to IPL Processing. Since Cu2NO3(OH)3 isn’t a thermally stable material, initially transformed into CuO. However, when fructose or glucose were intentionally included as additives in the inks, IPL Processing provided direct conversion of the Cu2(OH)3NO3 into Cu. Between the two sugars, fructose was more advantageous as it led to faster reduction and lower sheet resistances, with the lowest sheet resistance being 0.224 Ω/□.

Graphene oxide was reduced with Intense Pulsed Light Processing to explore potential towards scalable conductive films without the need for harsh/toxic reductants. The graphene oxide films on displayed a four magnitude decrease in sheet resistance from 55.1 MΩ/□. to 2280 Ω/□ after IPL. Plastic substrates required less energy to display reduction, with a four magnitude decrease in sheet resistance (62.5 MΩ/□. to 3.43 kΩ/□.) after IPL. When combined with Cu(OH)2 nanowires at weight percentages of 1.82%, 8.47%, and 32.65%, films exhibited decreased sheet resistances by 25%, 45%, and 66%, respectively.

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