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Published September 19, 2016 | Submitted + Published
Journal Article Open

Omnidirectional and broadband absorption enhancement from trapezoidal Mie resonators in semiconductor metasurfaces


Light trapping in planar ultrathin-film solar cells is limited due to a small number of optical modes available in the thin-film slab. A nanostructured thin-film design could surpass this limit by providing broadband increase in the local density of states in a subwavelength volume and maintaining efficient coupling of light. Here we report a broadband metasurface design, enabling efficient and broadband absorption enhancement by direct coupling of incoming light to resonant modes of subwavelengthscale Mie nanoresonators defined in the thin-film active layer. Absorption was investigated both theoretically and experimentally in prototypes consisting of lithographically patterned, two-dimensional periodic arrays of silicon nanoresonators on silica substrates. A crossed trapezoid resonator shape of rectangular cross section is used to excite broadband Mie resonances across visible and near-IR spectra. Our numerical simulations, optical absorption measurements and photocurrent spectral response measurements demonstrate that crossed trapezoidal Mie resonant structures enable angle-insensitive, broadband absorption. A short circuit current density of 12.0 mA/cm^2 is achieved in 210 nm thick patterned Si films, yielding a 4-fold increase compared to planar films of the same thickness. It is suggested that silicon metasurfaces with Mie resonator arrays can provide useful insights to guide future ultrathin-film solar cell designs incorporating nanostructured thin active layers.

Additional Information

© The Author(s). This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/ Received: 08 January 2016; Accepted: 27 June 2016; Published online: 19 September 2016. This work was supported by the Multidisciplinary University Research Initiative Grant (Air Force Office of Scientific Research, FA9550-12-1-0024) and used facilities supported by the DOE 'Light-Material Interactions in Energy Conversion' Energy Frontier Research Center under grant DE-SC0001293 and the Kavli Nanoscience Institute (KNI) at Caltech. We thank Dr. Dennis Callahan for helpful discussions. Author Contributions: R.A.P., K.A. and H.A.A. designed and conceived the experiments. R.A.P. fabricated the samples. R.A.P. developed the measurement setup. R.A.P. and S.B. performed the optical measurements. R.A.P. performed the photocurrent measurements. R.A.P. and S.B. performed numerical simulations. R.A.P., S.B., K.A. and H.A.A. wrote the paper. All authors discussed the results and commented on the manuscript. The authors declare no competing financial interests.

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Submitted - 1512.04305.pdf


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August 20, 2023
October 20, 2023