University of California, Riverside

Department of Electrical and Computer Engineering

Resonant Dielectric Structures for Photovoltaics and Polymer-metal Plasmonic Waveguides

Resonant Dielectric Structures for Photovoltaics and Polymer-metal Plasmonic....

Resonant Dielectric Structures for Photovoltaics and Polymer-metal Plasmonic Waveguides

February 13, 2012 - 2:00 pm
Winston Chung Hall, 205/206

Dr. Jonathan Grandidier


Light trapping is a critical requirement in thin film photovoltaics, and dielectric texturing is a viable method to induce light trapping, but thin film device quality often suffers upon direct texturing of the semiconductor active material. Thus it is de-sirable to develop a design method in which textured dielectric layers provide light trapping on smooth planar thin film cells. We propose here an approach for coupling light into smooth untextured thin film solar cells of uniform thickness us-ing periodic arrangements of resonant dielectric nanospheres deposited as a continuous film. Freely propagating sunlight can be diffractively coupled and transformed into several guided modes within the array of wavelength scale dielectric spheres. Incident optical power is then transferred to the thin film cell by leaky mode coupling into the cell's thin absorber layer. It is shown that guided whispering gallery modes in the spheres can be coupled into particular modes of the solar cell and significantly enhance its efficiency by increasing the fraction of incident light absorbed. We experimentally and numerically demonstrate this enhancement using full field finite difference time domain (FDTD) simulations of a nano-sphere array above a thin film solar cell structure featuring a back reflector and an anti-reflection coating.
Plasmonic waveguides enable transmission of both electrical and optical (plasmonic) signals in the same circuitry, and are therefore of great interest for integrated photonics applications. However, they suffer from strong plasmon losses due to dissipation in the metal film. We address here the possibility to compensate at telecom wavelengths the losses using a configuration analogous to an optical amplifier. A dielectric loaded surface plasmon polariton waveguide (DLSPPW) is doped with PbS quantum dots (QDs) emitting around λ = 1.5 μm. The SPP guided mode is excited at the telecom wave-length (λ = 1.55 μm) and an additional green laser pumps the QDs in their excited states. QD relaxation by stimulated emission of surface plasmon polaritons (SPPs) partially compensates intrinsic losses. DLSPPW mode propagation length and momentum are measured by leakage radiation microscopy in the image and Fourier planes respectively. The mode propagation length versus green pump irradiance demonstrates 27% increasing. A detailed analysis of the experimental data (in particular mode line width narrowing) and comparison with numerical simulations demonstrate the role of stimulat-ed emission of SPPs.
Biography: Jonathan Grandidier received his Ph.D. in physics from the University of Dijon, France, in 2009. He is cur-rently a Research Scientist in the Department of Applied Physics at the California Institute of Technology, Pasadena. His research interest is focused on new concepts for photovoltaics based on resonant dielectric structures. He received the SPIE Green Photonics Award in 2012 for pioneering contributions in the development of advanced technologies for the en-hancement of solar cell performance. His work is also centered on dielectric-loaded surface plasmon polariton waveguides for telecommunications. His work has been presented at international conferences and published in different international journals, and he has contributed chapters to one book.
Dr. Grandidier is a member of the International Society for Optics and Photonics (SPIE) and the Materials Research Society (MRS). He received a fellowship from the Carnot Foundation, where he has been a member since 2009.

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University of California, Riverside
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Electrical and Computer Engineering
Suite 343 Winston Chung Hall
University of California, Riverside
Riverside, CA 92521-0429

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