Micromachined silicon solar cells with micro-optic coupling features on the front surface
Micromachined silicon solar cells with micro-optic coupling features on the front surface
Interest in solar cell technology has increased over the years due mainly to a better understanding and improved processing technology of the semiconductor materials, the growing demand for non-polluting energy sources and also the increasing demand for powering of satellites and remote appliances. Silicon is the preferred semiconductor material because it is the most researched material in the electronics industry. Silicon is less absorbing in the long wavelength region and hence a fairly thick cell is required for total absorption. Thick cells however suffer from high minority carrier recombination but by texturing the cell surface to allow for oblique optical coupling and light trapping, it is possible to reduce the cell thickness without loss of adsorption whilst minimizing recombination.
The work presented in this thesis covers the theoretical considerations of a proposed method of coupling light into the silicon that results in longer optical path lengths, and also the design and fabrication of the structures which enable the realisation of this concept. This new method involves deflecting light rays on the silicon surface such that the coupled rays travel close to the surface. Successful implementation of this technique would make it possible to obtain high photocurrents from thin solar cells.
Two methods have been investigated. One involves the patterning of photoresist into microparabolic profiles on the silicon surface which can then be coated with a reflective material to form curved micromirrors. So far photoresist microparabolas have been fabricated and tested but further work is required for the integration into the solar cell systems. The other method uses a combination of microlenses and microreflectors which form a system that redirects normal incident light onto optical coupling areas on the silicon surface. The microlenses for this work were made by reflowing patterned photoresist and transfering the profile into quartz by ion beam milling. Fabricated solar cells with these micro-optic components have been tested and have been shown to be more effective for the long wavelength part of the spectrum.
University of Southampton
1998
Rotich, Samuel Kipkoske
(1998)
Micromachined silicon solar cells with micro-optic coupling features on the front surface.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Interest in solar cell technology has increased over the years due mainly to a better understanding and improved processing technology of the semiconductor materials, the growing demand for non-polluting energy sources and also the increasing demand for powering of satellites and remote appliances. Silicon is the preferred semiconductor material because it is the most researched material in the electronics industry. Silicon is less absorbing in the long wavelength region and hence a fairly thick cell is required for total absorption. Thick cells however suffer from high minority carrier recombination but by texturing the cell surface to allow for oblique optical coupling and light trapping, it is possible to reduce the cell thickness without loss of adsorption whilst minimizing recombination.
The work presented in this thesis covers the theoretical considerations of a proposed method of coupling light into the silicon that results in longer optical path lengths, and also the design and fabrication of the structures which enable the realisation of this concept. This new method involves deflecting light rays on the silicon surface such that the coupled rays travel close to the surface. Successful implementation of this technique would make it possible to obtain high photocurrents from thin solar cells.
Two methods have been investigated. One involves the patterning of photoresist into microparabolic profiles on the silicon surface which can then be coated with a reflective material to form curved micromirrors. So far photoresist microparabolas have been fabricated and tested but further work is required for the integration into the solar cell systems. The other method uses a combination of microlenses and microreflectors which form a system that redirects normal incident light onto optical coupling areas on the silicon surface. The microlenses for this work were made by reflowing patterned photoresist and transfering the profile into quartz by ion beam milling. Fabricated solar cells with these micro-optic components have been tested and have been shown to be more effective for the long wavelength part of the spectrum.
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Published date: 1998
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Local EPrints ID: 463510
URI: http://eprints.soton.ac.uk/id/eprint/463510
PURE UUID: ae83edb4-cac4-4eb3-86f5-f3cb403b8b1d
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Date deposited: 04 Jul 2022 20:52
Last modified: 04 Jul 2022 20:52
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Author:
Samuel Kipkoske Rotich
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