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Daniel J. Friedman
Researcher at National Renewable Energy Laboratory
Publications - 364
Citations - 12325
Daniel J. Friedman is an academic researcher from National Renewable Energy Laboratory. The author has contributed to research in topics: Solar cell & Band gap. The author has an hindex of 51, co-authored 322 publications receiving 11407 citations. Previous affiliations of Daniel J. Friedman include Georgia Institute of Technology & Bell Labs.
Papers
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Journal ArticleDOI
Band Anticrossing in GaInNAs Alloys
W. Shan,Wladek Walukiewicz,Joel W. Ager,Eugene E. Haller,J. F. Geisz,Daniel J. Friedman,J. M. Olson,Sarah Kurtz +7 more
TL;DR: In this paper, the authors present evidence for a strong interaction between the conduction band and a narrow resonant band formed by nitrogen states in alloys, which leads to a splitting of conduction bands into two subbands and a reduction of the fundamental band gap.
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40.8% efficient inverted triple-junction solar cell with two independently metamorphic junctions
J. F. Geisz,Daniel J. Friedman,J.S. Ward,Anna Duda,Waldo J. Olavarria,Tom Moriarty,J. Kiehl,Manuel J. Romero,Andrew G. Norman,Kim M. Jones +9 more
TL;DR: In this paper, a photovoltaic conversion efficiency of 40.8% at 326 suns concentration is demonstrated in a monolithically grown, triple-junction III-V solar cell structure in which each active junction is composed of an alloy with a different lattice constant chosen to maximize the theoretical efficiency.
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High-efficiency GaInP∕GaAs∕InGaAs triple-junction solar cells grown inverted with a metamorphic bottom junction
John F. Geisz,Sarah Kurtz,Mark Wanlass,J.S. Ward,Anna Duda,Daniel J. Friedman,J. M. Olson,William E. McMahon,Tom Moriarty,J. Kiehl +9 more
TL;DR: In this paper, a Ge-free III-V semiconductor triple-junction solar cell was presented, which achieved 33.8, 30.6, and 38.9% efficiencies under the standard 1sun global spectrum, space spectrum, and concentrated direct spectrum at 81suns, respectively.
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1-eV solar cells with GaInNAs active layer
TL;DR: In this paper, the authors demonstrate working prototypes of a GaInNAs-based solar cell lattice-matched to GaAs with photoresponse down to 1 eV. This device is intended for use as the third junction of future-generation ultrahigh-efficiency three and four-junction devices.
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III-N-V semiconductors for solar photovoltaic applications
J. F. Geisz,Daniel J. Friedman +1 more
TL;DR: In this paper, the main roadblock to the development of these solar cell devices is poor minority-carrier transport in the III-N-V materials, and the present understanding of the material properties of GaInNAs lattice matched to GaAs and GaNPAs matched to Si is reviewed.