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dc.contributor.advisorYu, Edward T.en
dc.creatorMcPheeters, Claiborne Otten
dc.date.accessioned2012-07-12T13:51:41Zen
dc.date.available2012-07-12T13:51:41Zen
dc.date.created2012-05en
dc.date.issued2012-07-12en
dc.date.submittedMay 2012en
dc.identifier.urihttp://hdl.handle.net/2152/ETD-UT-2012-05-5040en
dc.descriptiontexten
dc.description.abstractHigh efficiency photovoltaic solar cells are expected to continue to be important for a variety of terrestrial and space power applications. Solar cells made of optically thick materials often cannot meet the cost, efficiency, or physical requirements for specialized applications and, increasingly, for traditional applications. This dissertation investigates improving the performance of single-junction GaAs solar cells by incorporating InGaAs/GaAs quantum wells and quantum dots to increase their spectral response bandwidth, and by incorporating structures that confine light in the devices to improve their absorption of it. InGaAs/GaAs quantum dots-in-wells extend the response of GaAs homojunction devices to wavelengths >1200 nm. Nanoparticles that are randomly deposited on the top of optically thick devices scatter light into waveguide modes of the device structures, increasing their absorption of electromagnetic energy and improving their short-circuit current by up to 16%. Multiply periodic diffractive structures have been optimized using rigorous software algorithms and fabricated on the back sides of thin film quantum dot-in-well solar cells, improving their spectral response at wavelengths 850 nm to 1200 nm, where only the quantum dot-in-well structures absorb light, by factors of up to 10. The improvement results from coupling of diffracted light to waveguide modes of the thin film device structure, and from Fabry-Perot interference effects. Simulations of absorption in these device structures corroborate the measured results and indicate that quantum well solar cells of ~2 µm in thickness, and which are equipped with optimized backside gratings, can achieve 1 Sun Airmass 0 short-circuit current densities of up to ~5 mA/cm2 (15%) greater than GaAs homojunction devices, and of up to >2 mA/cm2 (7%) greater than quantum well devices, with planar back reflectors. A combination of Fabry-Perot interference and diffraction into waveguide modes of the thin devices is shown to dominate the simulated device response spectra. Simulations also demonstrate the importance of low-loss metals for realizing optimal light trapping structures. Such device geometries are promising for reducing the cost of high efficiency solar cells that may be suitable for a variety of traditional and emerging applications.en
dc.format.mimetypeapplication/pdfen
dc.language.isoengen
dc.subjectGaAsen
dc.subjectInAsen
dc.subjectInGaAsen
dc.subjectGaInAsen
dc.subjectSolar cellen
dc.subjectPhotovoltaicen
dc.subjectThin filmen
dc.subjectQuantum wellen
dc.subjectQuantum doten
dc.subjectLight trappingen
dc.subjectWaveguideen
dc.subjectNanoparticleen
dc.subjectDiffractionen
dc.subjectGratingen
dc.subjectScatteringen
dc.titleThe application of light trapping structures and of InGaAs/GaAs quantum wells and quantum dots to improving the performance of single-junction GaAs solar cellsen
dc.date.updated2012-07-12T13:52:02Zen
dc.identifier.slug2152/ETD-UT-2012-05-5040en
dc.contributor.committeeMemberAlu, Andreaen
dc.contributor.committeeMemberBank, Seth R.en
dc.contributor.committeeMemberChen, Ray T.en
dc.contributor.committeeMemberZhang, John X.en
dc.description.departmentElectrical and Computer Engineeringen
dc.type.genrethesisen
thesis.degree.departmentElectrical and Computer Engineeringen
thesis.degree.disciplineElectrical and Computer Engineeringen
thesis.degree.grantorUniversity of Texas at Austinen
thesis.degree.levelDoctoralen
thesis.degree.nameDoctor of Philosophyen


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