The NSERC Photovoltaic Innovation Network provided me with funding to present my research at the AVS 59th International Symposium from October 29 through November 2, 2012 in Tampa, Florida. AVS is a multidisciplinary society that connects researchers and industry focusing on vacuum science and applications. The conference facilitated sessions ranging from advanced surface science to applications of nanostructures in photovoltaic devices to new microscopy techniques. I found the conference to be extremely beneficial to my development as a researcher, and I would like to thank the NSERC Photovoltaic Innovation Network for providing me with a great opportunity.

My research involves the use of glancing angle deposition (GLAD) to improve the morphological control and crystal structure of branched nanowires, or nanotrees, grown through a vapour liquid solid (VLS) mechanism. I gave my first oral presentation at this conference, entitled, “Engineered Indium Tin Oxide (ITO) Nanowhiskers via Vapour Liquid Solid Glancing Angle Deposition (VLS-GLAD).” I presented in the GLAD section, which allowed me to present my research to experts in very closely related fields. The talk detailed the recent development of VLS-GLAD as a new technique to grow nanotrees. In addition, I presented results regarding the performance of electrodes composed of three-dimensional ITO nanotree architectures for application in organic photovoltaic devices (OPVs). ITO is a transparent conductive oxide commonly used as an electrode in OPVs. Nanostructured ITO electrodes have the potential to improve performance in OPVs by reducing charge extraction distances and increasing light absorption. The work I presented is a significant step towards controllable fabrication of such three-dimensional electrodes.

The above figure is a schematic of the VLS-GLAD mechanism.
During VLS-GLAD, the vapour flux is incident at oblique angles of deposition (alpha), which causes flux shadowing. Enhanced control over the number density and height dependent morphology of the structures is enabled using this technique.

The above figure shows indium tin oxide nanotree structures grown at various deposition rates using VLS-GLAD. The deposition rate was found to significantly effect the diameter and branching of the structures

I attended a wide variety of talks that were relevant to my research, as well as the NSERC Photovoltaic Innovation Network. Sections focussing on conductivity in nanowires and nanostructures were highly valuable in improving my understanding over complex transport in low dimensional structures. Talks focussing on the passivation of nanowire surfaces and new electrical characterization techniques will be extremely valuable in optimizing the conductivity of nanotree electrodes in my research. In addition, Harry Atwater gave an excellent talk entitled, “Photonic Materials for Solar Energy Conversion at the Thermodynamic Limit” which detailed the road forward for solar innovation. He spoke of the importance of the development of new solar technologies such as: light trapping, photon recycling, emission angle restriction and improved carrier thermalization. He stated that high efficiency versus low cost is a false dichotomy in current solar research and that the real goal is high efficiency AND low cost for widespread adoption of solar technology. Improved photon management to reduce entropic losses was laid out as an important step toward reaching optimal efficiency. Materials and device design have been studied thoroughly. However, Dr. Atwater suggests that more focus on photon management in devices through light trapping and spectrum splitting may lead to energy conversion at the thermodynamic limit.

The AVS 59th Symposium was beneficial to me as a new researcher, and my attendance was made possible by the NSERC Photovoltaic Innovation Network.

-Allan Beaudry (2nd year PhD student in Electrical & Computer Engineering, University of Alberta)

 

Allan was the winner of the second place and public choice awards for best research poster at the Next Generation Solar – Photovoltaics Canada – National Scientific Conference held May 14 and 15 in Montreal, Quebec.  His poster was on “Vapour Liquid Solid Glancing Angle Deposition of Indium tin Oxide Nanowhiskers”.  The awards take the form of funding for registration and travel to present a talk or poster at a prominent American or international scientific conference of the HQP’s choice.  Allan elected to present at the AVS 59th International Symposium.

Figures from:

Beaudry, A. L.; Tucker, R. T.; LaForge, J. M.; Taschuk, M. T.; Brett, M. J. Nanotechnology 2012, 23, 105608.

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