title: Multilayer-Grown Ultrathin Nanostructured GaAs Solar Cells as a Cost-Competitive Materials Platform for III-V Photovoltaics.
abstract: Large-scale deployment of GaAs solar cells in terrestrial photovoltaics demands significant cost reduction for preparing device-quality epitaxial materials. Although multilayer epitaxial growth in conjunction with printing-based materials assemblies has been proposed as a promising route to achieve this goal, their practical implementation remains challenging owing to the degradation of materials properties and resulting nonuniform device performance between solar cells grown in different sequences. Here we report an alternative approach to circumvent these limitations and enable multilayer-grown GaAs solar cells with uniform photovoltaic performance. Ultrathin single-junction GaAs solar cells having a 300-nm-thick absorber (i.e., emitter and base) are epitaxially grown in triple-stack releasable multilayer assemblies by molecular beam epitaxy using beryllium as a p-type impurity. Microscale (∼500 × 500 μm2) GaAs solar cells fabricated from respective device layers exhibit excellent uniformity (<3% relative) of photovoltaic performance and contact properties owing to the suppressed diffusion of p-type dopant as well as substantially reduced time of epitaxial growth associated with ultrathin device configuration. Bifacial photon management employing hexagonally periodic TiO2nanoposts and a vertical p-type metal contact serving as a metallic back-surface reflector together with specialized epitaxial design to minimize parasitic optical losses for efficient light trapping synergistically enable significantly enhanced photovoltaic performance of such ultrathin absorbers, where ∼17.2% solar-to-electric power conversion efficiency under simulated AM1.5G illumination is demonstrated from 420-nm-thick single-junction GaAs solar cells grown in triple-stack epitaxial assemblies.
authors.forename: Boju
authors.initials: B
authors.lastname: Gai
authors.affiliation: Department of Electrical Engineering, Yale University , New Haven, Connecticut 06520, United States.|Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.
authors.forename: Yukun
authors.initials: Y
authors.lastname: Sun
authors.forename: Haneol
authors.initials: H
authors.lastname: Lim
authors.forename: Huandong
authors.initials: H
authors.lastname: Chen
authors.affiliation: Department of Electrical Engineering, Yale University , New Haven, Connecticut 06520, United States.
authors.forename: Joseph
authors.initials: J
authors.lastname: Faucher
authors.affiliation: Department of Electrical Engineering, Yale University , New Haven, Connecticut 06520, United States.|Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.
authors.forename: Minjoo L
authors.initials: ML
authors.lastname: Lee
authors.forename: Jongseung
authors.identifier: 0000-0001-5342-1181
authors.initials: J
authors.lastname: Yoon
keywords: III−V solar cells; bifacial photon management; multilayer epitaxial assemblies; transfer printing; ultrathin gallium arsenide