title: Energy Harvesting for GaAs Photovoltaics Under Low-Flux Indoor Lighting Conditions.
abstract: GaAs photovoltaics are promising candidates for indoor energy harvesting to power small-scale (≈1 mm2) electronics. This application has stringent requirements on dark current, recombination, and shunt leakage paths due to low-light conditions and small device dimensions. The power conversion efficiency and the limiting mechanisms in GaAs photovoltaic cells under indoor lighting conditions are studied experimentally. Voltage is limited by generation-recombination dark current attributed to perimeter sidewall surface recombination based on the measurements of variable cell area. Bulk and perimeter recombination coefficients of 1.464 pA/mm2and 0.2816 pA/mm, respectively, were extracted from dark current measurements. Resulting power conversion efficiency is strongly dependent on cell area, where current GaAs of 1-mm2indoor photovoltaic cells demonstrates power conversion efficiency of approximately 19% at 580 lx of white LED illumination. Reductions in both bulk and perimeter sidewall recombination are required to increase maximum efficiency (while maintaining small cell area near 1 mm2) to approach the theoretical power conversion efficiency of 40% for GaAs cells under typical indoor lighting conditions.
authors.affiliation: Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109 USA.
authors.forename: Alan S
authors.initials: AS
authors.lastname: Teran
authors.affiliation: Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109 USA.
authors.forename: Eunseong
authors.initials: E
authors.lastname: Moon
authors.affiliation: Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109 USA.
authors.forename: Wootaek
authors.initials: W
authors.lastname: Lim
authors.affiliation: Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109 USA.
authors.forename: Gyouho
authors.initials: G
authors.lastname: Kim
authors.affiliation: Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109 USA.
authors.forename: Inhee
authors.initials: I
authors.lastname: Lee
authors.affiliation: Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109 USA.
authors.forename: David
authors.initials: D
authors.lastname: Blaauw
authors.affiliation: Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109 USA.
authors.forename: Jamie D
authors.initials: JD
authors.lastname: Phillips
keywords: Compound semiconductors; diodes; electronic devices; recombination