Title:
Investigation of Light Induced Degradation in Promising Photovoltaic Grade Si and Development of Porous Silicon Anti-Reflection Coatings for Silicon Solar Cells

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dc.contributor.advisor Rohatgi, Ajeet
dc.contributor.author Damiani, Benjamin Mark en_US
dc.contributor.committeeMember James Gole
dc.contributor.committeeMember Miroslav Begovic
dc.contributor.committeeMember Gaylord, Thomas K.
dc.contributor.committeeMember W. Russ Callen
dc.contributor.department Electrical and Computer Engineering en_US
dc.date.accessioned 2005-03-03T22:03:34Z
dc.date.available 2005-03-03T22:03:34Z
dc.date.issued 2004-04-16 en_US
dc.description.abstract Cast multi-crystalline silicon substrates are used in more than 50% of the photovoltaic modules produced today. The random grain orientations of multi-crystalline silicon wafers inhibit the formation of an effective surface texturing using conventional techniques. The other main substrate used is single crystalline Czochralski wafers (~30% of the market share). Czochralski silicon material is known to suffer from the formation of a metastable defect under carrier injection, sometimes referred to as light induced degradation (LID). Light induced degradation in low-cost photovoltaic grade silicon is studied. Trap formation is shown to occur at temperatures above 200oC. Efficiency degradation reduced from 0.75% to 0.24% when the cell thickness was reduced from 378 to 157m. The presence of light induced degradation in ribbon silicon solar cells is documented for the first time in this thesis. Trap generation and annihilation are observed in high lifetime regions of multi-crystalline silicon samples. No degradation was observed over a 24-hour period at 25oC in high efficiency ribbon solar cells (>16%), but at an elevated temperature of ~75oC, appreciable efficiency degradation was observed. Czochralski silicon solar cells showed full degradation within 24 hours at 25o C. Part two of this thesis involves the development of a surface texturing suitable for all crystalline silicon. Only 6 to 10 seconds in a 200:1 HF to HNO3 solution at room temperature allows for the formation of an effective porous silicon anti-reflection coating. This resulted in a porous silicon anti-reflection coated solar cell efficiency of 15.3% on a float zone Si sample with an excellent fill factor (78.7%). The typical process used in the literature involves porous silicon etching as the final step in the solar cell fabrication sequence. The major problem associated with this process sequence is fill factor degradation. This problem was overcome in this research by porous silicon etching prior to cell processing. It is shown that incorporating an acid texture prior to porous silicon etching can improve the surface reflectance for cast multi-crystalline and Czochralski silicon samples. Solar cell efficiencies of 14.8% for Cz Si and 13.6% for cast mc-Si were achieved. en_US
dc.description.degree Ph.D. en_US
dc.format.extent 2031530 bytes
dc.format.mimetype application/pdf
dc.identifier.uri http://hdl.handle.net/1853/5203
dc.language.iso en_US
dc.publisher Georgia Institute of Technology en_US
dc.subject Texture en_US
dc.subject Porous
dc.subject Degradation
dc.subject Multi-crystalline
dc.subject Czochralski
dc.subject Screen-printed
dc.title Investigation of Light Induced Degradation in Promising Photovoltaic Grade Si and Development of Porous Silicon Anti-Reflection Coatings for Silicon Solar Cells en_US
dc.type Text
dc.type.genre Dissertation
dspace.entity.type Publication
local.contributor.advisor Rohatgi, Ajeet
local.contributor.corporatename School of Electrical and Computer Engineering
local.contributor.corporatename College of Engineering
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relation.isOrgUnitOfPublication 5b7adef2-447c-4270-b9fc-846bd76f80f2
relation.isOrgUnitOfPublication 7c022d60-21d5-497c-b552-95e489a06569
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