Journal of Materials Research

Invited Feature Papers

Enhancement of solar cells with photonic and plasmonic crystals - overcoming the Lambertian limit

Rana Biswasa1 c1, Sambit Pattnaika2, Chun Xua3, Joydeep Bhattacharyaa4, Nayan Chakravartya4 and Vikram Dalala4

a1 Department of Physics and Astronomy and Ames Laboratory, Iowa State University, Ames, Iowa 50011; and Microelectronics Research Center and Department of Electrical and Computer Engineering, Iowa State University, Ames, Iowa 50011

a2 Microelectronics Research Center and Department of Electrical and Computer Engineering, Iowa State University, Ames, Iowa 50011

a3 Department of Physics and Astronomy and Ames Laboratory, Iowa State University, Ames, Iowa 50011

a4 Microelectronics Research Center and Department of Electrical and Computer Engineering, Iowa State University, Ames, Iowa 50011

Abstract

Red and near-infrared photons of longer wave lengths are poorly absorbed in thin film silicon cells and advanced light trapping methods are necessary. The physical mechanisms underlying the light trapping using periodic back reflectors are strong light diffraction, coupled with plasmonic light concentration. These are contrasted with the scattering mechanisms in randomly textured back reflectors. We describe a class of conformal solar cells with nanocone back reflectors with absorption at the Lambertian 4n2 limit, averaged over the “entire” wave length range for hydrogenated nanocrystalline silicon (nc-Si:H) thin-film solar cells. The absorption is theoretically found for 1-μm nc-Si:H cells, and is further enhanced for off-normal incidence. Predicted currents exceed 31 mA/cm2. Nc-Si:H solar cells with the same device architecture were conformally grown on periodic substrates and compared with randomly textured substrates. The periodic back reflector solar cells with nanopillars demonstrated higher quantum efficiency and photocurrents that were 1 mA/cm2 higher than those for the randomly textured back reflectors.

(Received September 01 2012)

(Accepted February 08 2013)

Correspondence

c1 Address all correspondence to this author. e-mail: biswasr@iastate.edu

Footnotes

  This paper has been selected as an Invited Feature Paper.

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