Much of our group's work involves the synthesis, characterization, and device integration of nanowires. Their size and high aspect ratio geometry leads to a variety of technologically useful properties such as large surface area, quantum confinement of electrons, large piezoresistance, high thermoelectric conversion efficiency, and facile elastic strain relaxation. Because of these properties and the availability of simple and cost-effective methods for their synthesis, nanowires are attractive candidates for a range of electronic, optical, sensing, and energy device applications, such as transistors, sensors, lithium-ion battery anodes, solar cells, and thermoelectric devices. Furthermore, single-crystalline, defect-free nanowires can be deposited on a variety of substrates (amorphous, transparent, flexible, etc.) without the requirement of a potentially expensive lattice-matched single-crystalline substrate.
Transparent electrodes are a necessary component in a number of electronic and optoelectronic devices such as liquid crystal displays, touch screens, solar cells, and organic light emitting diodes (OLEDs). The most commonly used transparent conductor, indium tin oxide (ITO), is expensive, has limited mechanical flexibility, and requires sputtering, high temperatures, and vacuum for deposition. Recent advances in nanomaterials have generated alternatives to ITO. We have demonstrated that films consisting of random networks of solution-synthesized silver nanowires have transparency and conductivity values better than competing new flexible technologies (eg. carbon nanotube films, graphene) and comparable to ITO. These silver nanowire films are cheap, flexible, and compatible with roll-to-roll deposition techniques. We have tackled the problem of surface roughness and have reduced the root-mean-square roughness to 7 nm, with a maximum peak-to-valley of < 30 nm. Our electrodes have been successfully used in switchable privacy glass and solar cells. However, in the latter case, we have shown that the electrode lifetime is unacceptable. We are currently working to improve lifetimes for solar cell applications.
Electronic textiles, where electronic devices are integrated with threads and fabrics, is an emerging area with capabilities ranging from health monitoring to energy
generation. Because single-crystalline nanowires can be synthesized in solution and easily transferred to arbitrary substrates, they are an excellent material for e-textiles.
We have coated the surface of cotton, polyester, and nylon threads with meshes of silver nanowires to render them electrically conductive, at a material cost of less than 4 cents/metre.
These conductive threads are more flexible and lighter-weight than conventional conductive thread.
Conductive fabrics have also been fabricated. Because nanowires of many different semiconductor and metallic
materials can be synthesized, there is a wide range of e-textile devices they can enable.
See an article about Prof. Goldthorpe's group research in this area here.
We have developed a simple, low cost method to align metal and semiconductor nanowires over large areas. Nanowire assembly techniques are required for the integration of solution synthesized nanowires into devices, as well as to obtain certain functionality such as the ability to polarize light.
The electrical transport properties of nanowires are often different than their bulk material counterparts due to their size, shape, and high surface area. Although a multitude of different types of nanowires have been synthesized and incorporated into various devices, data concerning their electrical properties are often lacking because the probing of individual nanowires is not a trivial matter. We are currently investigating the transport properties of individual metallic and semiconductor nanowires through 4-point probe measurements. In doing so we are elucidating the properties of these nanowires, assessing their viability for particular applications, and guiding parameters for their improved synthesis.