Prospects for concentrating photovoltaic (CPV) power are growing as the market increasingly values high power conversion efficiency to leverage now-dominant balance of system and soft costs. This trend is particularly acute for rooftop photovoltaic power, where delivering the high efficiency of traditional CPV in the form factor of a standard rooftop photovoltaic panel could be transformative. Here, we demonstrate a fully automated planar microtracking CPV system <2 cm thick that operates at fixed tilt with a microscale triple-junction solar cell at >660× concentration ratio over a 140 full field of view. In outdoor testing over the course of two sunny days, the system operates automatically from sunrise to sunset, outperforming a 17%-efficient commercial silicon solar cell by generating >50% more energy per unit area per day in a direct head-to-head competition. These results support the technical feasibility of planar microtracking CPV to deliver a step change in the efficiency of rooftop solar panels at a commercially relevant concentration ratio.

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This work was funded in part by the Advanced Research Projects Agency-Energy (ARPA-E) MOSAIC program, US Department of Energy, under Award No. DE-AR0000626 and by the National Science Foundation under Grant No. CBET-1508968. J.H. and R.G.N. were supported as part of the Department of Energy ‘Light-Material Interactions in Energy Conversion Energy Frontier Research Center’ under grant DE-SC0001293.

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Author notes

    • Jared S. Price
    • , Alex J. Grede
    •  & Baomin Wang

    These authors contributed equally to this work.


  1. Department of Electrical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA

    • Jared S. Price
    • , Alex J. Grede
    • , Baomin Wang
    • , Michael V. Lipski
    •  & Noel C. Giebink
  2. Semprius Inc., 4915 Prospectus Drive, Suite C, Durham, North Carolina 27713, USA

    • Brent Fisher
    •  & Scott Burroughs
  3. Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA

    • Kyu-Tae Lee
    •  & John A. Rogers
  4. Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA

    • Junwen He
    •  & Ralph G. Nuzzo
  5. Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA

    • Gregory S. Brulo
    • , Xiaokun Ma
    •  & Christopher D. Rahn


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J.S.P. designed and characterized the optics, designed the test jig for the CPV system, and performed the thermal simulations. A.J.G. wrote the outdoor testing software, and A.J.G. and M.V.L. wrote the tracking algorithm. B.W. designed and deposited all of the optical coatings and simulated the manufacturing and thermal tolerances of the system. Outdoor testing was carried out by all of the aforementioned authors. B.F. and S.B. supplied the 3J μPV cells for field testing, while K.-T.L., J.H., R.G.N. and J.A.R. supplied the GaAs μPV cells for concentrator optical efficiency measurements in the laboratory. G.S.B., X.M. and C.D.R. conceived the module design. N.C.G. supervised the project. J.S.P. and N.C.G. wrote the manuscript in consultation with all of the authors.

Competing interests

The authors declare that B.F., S.B. and J.A.R. (affiliated with Semprius) are involved in commercializing technologies related to those described here. J.A.R. is a co-founder of Semprius.

Corresponding author

Correspondence to Noel C. Giebink.

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