Materials Science Seminar: Improving sub-bandgap carrier collection in GaAs solar cells
Improving sub-bandgap carrier collection in GaAs solar cells by optimizing InGaAs quantum wells using strain-balancing and distributed Bragg reflectors
Brandon Bogner
Materials Science and Engineering MS Candidate
School of Chemistry and Materials Science, RIT
Mr. Bogner will discuss the effects of InxGa1-xAs quantum wells on GaAs-based solar cells with the goal of increasing current production while mitigating losses to open-circuit voltage. The discussed devices were grown, fabricated and characterized at RIT with funding provided by Magnolia Optical and the Indian Space Research Organization.
This event will be held on campus in 1125 Carlson Hall or you may join via Zoom at the link below.
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Abstract:
III-V materials have proven to be high-efficient, low-weight PV devices given their direct bandgaps and flexibility of lattice constant and bandgap through alloying. Bulk carrier collection in GaAs solar cells, a staple III-V PV material, is limited by the GaAs bandgap of 1.42eV, leaving low-energy photons below 1.42eV uncollected. The addition of low bandgap materials in GaAs-based devices allows for the collection of these ‘unreachable’ photons. The low bandgap material of choice is an InxGa1-xAs alloy, providing bandgaps of 0.354-1.42eV based on indium composition, allowing for tunable collection at longer wavelengths. Including thin 9.2nm InxGa1-xAs quantum wells in the i-region of a GaAs n-i-p device enhances photon collection past the 870nm GaAs band edge, increasing current production and potentially leading to higher efficiencies. Increased current production in GaAs solar cells is especially valuable since GaAs is used as a mid-junction cell in triple junction InGaP-GaAs-Ge structures common in space PV applications, where current-matching between the three sub-cells is vital for reaching efficiencies above 40% under solar concentration. To prevent accumulation of strain due to the differences in the GaAs and InxGa1-xAs lattice constants, GaAs1-yPy strain-balanced barriers are added on both sides of the InxGa1-xAs wells. The effects of incorporating InGaAs-GaAsP superlattices in the junction on device performance are investigated, with a focus on open-circuit voltage and sub-bandgap current collection as alloy composition and well number are varied.
Speaker Bio:
Brandon is a BS/MS student in the Materials Science department with a Bachelor of Science in Physics. His research interests surround solid-state technology and microelectronics, specifically photovoltaic devices. Outside of research, Brandon enjoys hiking, rock climbing and Brazilian Jiu Jitsu. In the future, he hopes to continue work in the PV industry then transition to a career in teaching.
Intended Audience:
Undergraduates, graduates, and experts. Those with interest in the topic.
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Open to the Public
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No