Document Type

Thesis - University Access Only

Award Date

2008

Degree Name

Master of Science (MS)

Department / School

Electrical Engineering and Computer Science

Abstract

By increasing the efficiency and/or by reducing the material cost it is possible to decrease the levelized energy cost (LEC) of photovoltaics and make it competitive against fossil fuels as primary source of energy. Among several concepts suggested for achieving high efficiency is the concept of spectral conversion based solar cells. The concept is to modify the incident spectra to match the solar cell thereby reducing the losses and increasing the efficiency. There are two spectral conversion based approaches; down-conversion and up-conversion. Objective of this thesis was to analyze the up conversion based solar cells (UCSC) to assess their promise. To that end, a photon counting model was developed and used to analyze such solar cells. Similarly, existing models for calculating the radiative limit of efficiency of UCSCs were extended by I) relaxing the requirement that the solar cell and the up-converter have the same refractive index; 2) accommodating different level of antireflection across the ambient and solar cell and solar cell and the up-converter interface in the model. The modified models were then again used to analyze the UCSCs. In the process an accurate and reliable method for photon and energy flux calculation was also developed. Photon counting model showed that more than 20% absolute improvement in efficiency above that achievable using single junction solar cells is possible. The radiative model too shows an efficiency improvement of more than 15% absolute. It further shows that the optimum bandgap values are around 2 e V and that large values of refractive indices are preferred if good antireflection coatings are used. Similarly, matching the refractive indices of the solar cell and the up-converter is found to be beneficial.

Library of Congress Subject Headings

Solar cells

Photovoltaic power generation

Format

application/pdf

Number of Pages

140

Publisher

South Dakota State University

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