Joshua Cottom

Project Title: Enhancing Solar Energy Conversion Using Nanotechnology

Background

I graduated from the University of Leeds in 2012 with an integrated BEng / MEng in Energy and Environmental Engineering with first class honours achieved in both. This degree fuelled my passion for renewable technologies and the challenges associated with stopping climate change, leading me on to join the DTC in low carbon technologies. For my undergraduate dissertation I designed a theoretical biomass torrefaction plant that could use the volatile compounds given off to power the process. Alternatively, for my master’s dissertation I researched the use of novel catalysts in the chemical looping steam reforming of methane in order to produce hydrogen in a more environmentally friendly manner. I have also worked as a researcher for the company Energy Management Systems whereby I determined the energy savings achieved using voltage optimisation on a variety of appliances.

My Research - Background to Plasmonics

My research involves the use of plasmonic effects to increase solar energy conversion. Plasmonic effects occur when light interacts with metallic nanoparticles that are much smaller than the wavelength of light. A collective oscillation of the valance electrons occurs at certain frequencies depending on a number of controllable variables such as the metal used, the geometry and its surrounding dielectric environment. By carefully manipulating these conditions the plasmon resonance can be tuned to occur at advantageous wavelengths such as in the visible region.

The plasmonic resonance offers a number of advantages for solar energy conversion. Firstly they act as nanoanntenna whereby they absorb incident electromagnetic waves with an absorption cross section greater than their geometric equivalent. Similarly the plasmonic nanoparticles may also increase the scattering of the light, thereby leading to larger pathlengths in solar cells. Crucially however, plasmonic metal nanoparticles give a large increase in the near field electric field, particularly when multiple particles are coupled together with small separation distances.

The above effects have many applications however particular interest lies in using the nanoparticles to improve the efficiencies of solar cells and photocatalytic reactions. This may be done by using the increased near field enhancements and improved cross sections to gain absorption in an adjacent semiconductor. For thin film solar cells this allows improved absorption compared to their optical thickness, where as when used in photocatalytic applications, they allow absorption in regions typically not associated with suitable semiconductors (i.e. visible absorption for TiO2).

PhD Project

As mentioned above, my research is looking at using the plasmonic effects of metallic nanoparticles to enhance solar energy conversion.

I aim to do this by creating an template electrochemically deposited array of gold nanorods with a semiconductor coating to enhance photocatalytic reactions such as water splitting for hydrogen production. I may also use this array for photovoltaic purposes.

Along side this, I am also using the computer software COMSOL multiphysics to simulate the plasmon resonances of various metallic nanoparticles with the hope of determining geometries and conditions in which the resonance can be optimised.