Delaina A. Amos

Room Temperature Synthesis of a Copper Ink for the Intense Pulsed Light Sintering of Conductive Copper Films

Conducting films are becoming increasingly important for the printed electronics industry with applications in various technologies including antennas, RFID tags, photovoltaics, flexible electronics, and displays. To date, expensive noble metals have been utilized in these conductive films, which ultimately increases the cost. In the present work, more economically viable copper based conducting films have been developed for both glass and flexible PET substrates, using copper and copper oxide nanoparticles. The copper nanoparticles (with copper(I) oxide impurity) are synthesized by using a simple copper reduction method in the presence of Tergitol as a capping agent. Various factors such as solvent, pH, and reductant concentration have been explored in detail and optimized in order to produce a nanoparticle ink at room temperature. Second, the ink obtained at room temperature was used to fabricate conducting films by intense pulse light sintering of the deposited films. These conducting films had sheet resistances as low as 0.12 Ω/□ over areas up to 10 cm(2) with a thickness of 8 μm.

Nanowire architectures for iodide free dye-sensitized solar cells

In this study, we show that the performance of iodide free redox couples in dye-sensitized solar cells could be significantly improved by engineering the electron transport and surface properties of the electrode materials. Specifically, tin oxide nanowires electrophoretically coated with titania nanoparticles and subsequently passivated with a submonolayer of alumina by atomic layer deposition show a remarkable ten-fold increase in short-circuit current densities over those obtained with titania nanoparticles, even when a typical N-719 dye is used for sensitization. Comparison of the performance of different electrode materials such as nanowires, nanoparticles and nanowire–nanoparticle hybrid architectures of tin oxide and titania suggests that fast electron transport helps in improving the short-circuit current density with ferrocene/ferrocenium and TEMPO redox couples. The nature of the surface trap states and their passivation have a significant effect on the electron lifetimes in the semiconductor and the resulting open-circuit voltage with these redox couples. The higher electron diffusion lengths with the tin oxide nanowire based architectures allow for thicker electrodes with enhanced dye loading. The analysis of literature data on DSCs made using different dyes and alternate redox couples suggests smaller delta G or reorganization energy for non-ruthenium based dyes.

Seed mediated copper nanoparticle synthesis for fabricating oxidation free interdigitated electrodes using intense pulse light sintering for flexible printed chemical sensors

A facile aqueous-based seed-mediated chemical reduction method is developed for the synthesis of copper nanoparticles. The nanoparticles are utilized to fabricate a flexible chemical sensor. The seed particles are spherical in shape with a mean diameter of 4.5 nm. Seed mediated growth is carried-out on the seed particles using L-ascorbic acid as a reducing and a capping agent in an aqueous solution. The seed mediated growth yields pure copper nanoparticles with a bimodal size distribution with mean diameters of 3.6 and 64.6 nm. The structural characterization, using X-ray diffraction (XRD) and UV-Visible spectroscopy (UV-Vis), reveals that the synthesized particles are oxidation free and exhibit a monotonic surface plasmon resonance (SPR) peak at 572 nm. The formulated nanoparticulate ink is printed on a flexible polyethylene terephthalate (PET) substrate and sintered with an intense pulse light (IPL) technique under ambient conditions resulting in an oxidation-free copper film within a milli-second time scale. The sheet resistance of the sintered film reaches 0.16 Ω □−1 yielding a film resistivity of 9.6 × 10−5 Ω cm. The as-synthesized particles are further employed to print interdigitated electrode patterns on a PET substrate using a syringe dispensing system. A chemical sensor is fabricated on the interdigitated electrodes using a novel graphite and polyethylene glycol (PEG) composite film. The chemical sensor exhibits an excellent response with up to 300 times change in the initial resistance when exposed to different concentrations of ethanol vapors, which demonstrates the potential of utilizing the copper nanoparticles developed in this study for flexible printed electronics applications.

Printed hybrid quantum dot light-emitting diodes for lighting applications

Novel quantum dot (QD) materials are explored to generate light and color. Inkjet printing of a QD single layer hybrid device is used to generate light. The QD/conjugated polymer interface is controlled via ligand attachments.

Engineering the Photoanode Using Scalable Hybrid Nanostructures

Dye sensitized solar cells (DSSCs) have garnered a great deal of interest as a cost-effective technology for large-scale manufacturing. Engineered inorganic hybrid nanostructures can improve the performance of DSSC’s without affecting the cost effectiveness of the devices. Here, we present a concept of engineered hybrid nanostructures, incorporating appropriate selection of nanowire and nanoparticle materials, to enhance the charge transport and reduce the recombination within the photoanode. Low recombination properties of this photoanode allow flexibility in choosing the redox couple for increasing open circuit voltage.Copyright