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Characterization and modeling of CdCl2 treated CdTe/CdS thin-film solar cells

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dc.contributor.authorMaxwell, Graham Lane, author
dc.contributor.authorManivannan, Venkatesan, advisor
dc.contributor.authorSampath, W. S., committee member
dc.contributor.authorSites, James R., committee member
dc.date.accessioned2007-01-03T08:12:29Z
dc.date.available2007-01-03T08:12:29Z
dc.date.issued2010
dc.description.abstractCdTe photovoltaic technology has the potential to become a leading energy producer in the coming decades. Its physical properties are well suited for photovoltaic energy conversion. A key processing step in the production of high efficiency CdTe/CdS solar cells is a post-CdTe deposition heat treatment with CdCl2, which can improve performance by promoting CdTe recrystallization, QE response, defect passivation and others. Understanding the effects of the CdCl2 treatment is crucial in order to optimize processing conditions and improve performance. This study investigates the effects of variations of CdCl2 treatment duration on CdTe/CdS solar cells manufactured at Colorado State University. In order to investigate the optimal time of CdCl2 treatment, sample solar cells were tested for microstructural and performance properties. Device microstructure was analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Device performance was analyzed using current density-voltage (J-V) measurements, time-resolved photoluminescence (TRPL), quantum efficiency (QE), and laser beam induced current (LBIC) measurements. Little change in microstructure was observed with extended CdCl2 treatment and is attributed to the high CdTe deposition temperatures used by heat pocket deposition (HPD). This deposition technique allows for large initial grains to be formed with low lattice strain energy which prevents recrystallization and grain growth that is often seen with other deposition techniques. The CdCl2 treatment initially improves performance significantly, but it was shown to that extending the CdCl2 treatment can reduce performance. Overall performance was reduced despite an increase in minority carrier lifetime values. The mechanism of reduced performance is suggested to be the formation of a low bandgap CdTe layer resulting from sulfur diffusion from the CdS layer. Sulfur diffusion primarily occurs during the CdCl2 treatment and also leads to thinning of the CdS layer. Solar cell modeling was employed to investigate possible mechanisms for performance degradation. Modeling was done with AMPS and SCAPS modeling software. Models were created to investigate the effects of minority carrier lifetime, CdS thickness, and a low bandgap CdTe layer. Modeling results showed that the formation of a low bandgap CdTe layer combined with CdS thinning reduces device performance. Further research is needed using a statistically significant number of samples to investigate other possible degradation mechanisms associated with extended CdCl2 treatment.
dc.format.mediumborn digital
dc.format.mediummasters theses
dc.identifierMaxwell_colostate_0053N_10110.pdf
dc.identifierETDF2010400366MCEN
dc.identifier.urihttp://hdl.handle.net/10217/68386
dc.languageEnglish
dc.language.isoeng
dc.publisherColorado State University. Libraries
dc.relation.ispartof2000-2019
dc.rightsCopyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.
dc.subjectCdCl2
dc.subjectCdS
dc.subjectCdTe
dc.subjectcharacterization
dc.subjectmodeling
dc.subjectsulfur
dc.titleCharacterization and modeling of CdCl2 treated CdTe/CdS thin-film solar cells
dc.typeText
dcterms.rights.dplaThis Item is protected by copyright and/or related rights (https://rightsstatements.org/vocab/InC/1.0/). You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).
thesis.degree.disciplineMechanical Engineering
thesis.degree.grantorColorado State University
thesis.degree.levelMasters
thesis.degree.nameMaster of Science (M.S.)

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