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Nanopillar Photovoltaics: Photon Management and Junction Engineering for Low-cost Solar Cells

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What
  • PhD Defenses
When Nov 20, 2013
from 02:00 PM to 04:00 PM
Where Engr. IV Bldg, Tesla Room 53-125
Contact Name
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Giacomo Mariani

Advisor: Prof. Diana L. Huffaker

 

Abstract

Solar electricity represents an unlimited and environmentally-benign source of power. However, it is still more than twice as expensive as natural gas-fired generators. III-V semiconductor nanostructures, defined as nanopillars, hold the promise to aggressively diminish the cost of the active photovoltaic cell by exploiting a fraction of material utilized in conventional planar schemes.

This talk focuses on two classes of high-performance nanopillar-based solar cells. The first configuration incorporates conjugated polymers to achieve a hybrid organic/inorganic heterojunction. That combines a high optical absorption arising from the polymeric layer in conjunction with an efficient carrier transport resulting from the semiconductor nanopillar array. The controllability of the heterojunction properties is achieved through electropolymerization which tunes the electrical conductivity and energy levels of the polymer achieving 4.11% conversion efficiency. The second class of solar cells is based on all-semiconductor radial p-n homojunctions embedded in nanopillars. Ex-situ and in-situ surface passivations are compared to alleviate the recombination effects cause by surface states on the junction. The photon coupling is maximized by adopting a dome morphology of the transparent top contact. The particular shape is found to concentrate and intensify the optical field within the active nanopillar volume, resulting into resonance peaks in the quantum yield measurements, at 7.43% efficiency.

 

Biography

Giacomo Mariani is a Ph.D. candidate in UCLA Electrical Engineering Department. His research interests are in semiconductor nanomaterials to investigate light-matter interactions for efficient solar conversion in next-generation photovoltaics. He earned his B.S. and M.S. degree in Electrical Engineering from University of Bologna, in 2006 and 2008, respectively.

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