Date of Award

Spring 4-1-2015

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Electrical, Computer & Energy Engineering

First Advisor

Wounjhang Park

Second Advisor

Xiaobo Yin

Third Advisor

Garret Moddel

Fourth Advisor

Sean Shaheen

Fifth Advisor

Milos Popovic

Abstract

This thesis studies the application of plasmonics in solar energy conversion and near field thermal energy harvesting.

The efficiency of semiconductor solar cell is limited by the inability of absorbing photons with energy below the bandgap. By designing plasmonic nanograting with resonance at the absorption edge, ~10% overall absorption improvement is achieved. Both localized and propagating surface plasmon modes are observed in the device. Their interaction, and the influence on overall solar cell absorption performance are studied in details.

In addition, this thesis studies the upconversion materials which can convert unabsorbed near infrared photons by semiconductor solar cells into well absorbed visible photons. By tuning the surface plasmon resonance at the upconversion frequency with silver nanograting structure, the photoluminescence of upconversion material can be improved by 39-fold maximum. The rate equation analysis reveals that the improvement is attributed to roughly 3-fold absorption enhancement and 2-fold energy transfer enhancement with plasmonics.

This thesis also explores the application of plasmonics to enhanced near field thermal radiation harvesting. I designed metamaterial to excite the spoof surface plasmon in the terahertz frequency for strongly enhanced thermal radiation. The FDTD simulation developed from the fluctuation electrodynamics demonstrates several hundredfold enhancement of thermally excited electromagnetic energy in the near field.

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