Case 09355

Super prism back reflector for thin film solar cells to accommodate large angle reflection of light


Thin crystalline silicon solar cell, photonic structure, photonic band gap, backside reflector, light trapping, Lambertian surface, photonic density, void array formation, internal quantum efficiency


Bulk, thin polycrystalline films on silicon or other substrate materials


Conversion efficiency of photons to carriers due to short optical path length in the crystalline silicon cells


The photonic crystal backside reflector described herein reduces problems with light trapping in thin crystalline silicon solar cells. The novel solar cell consists of a photoactive region, a Lambertian surface on the top side of the photoactive region, and a photonic crystal on the backside of the photoactive region. The backside reflector is in the form of a super prism structure, and allows for large angle reflection of light due to anomalous dispersion created by the photonic crystals. Processing of the super prism structure is based on plasma etching for via-hole fabrication and annealing.

  • Enhances absorption of photons with near band-edge energies
  • Cost-effective silicon processing methods to prototype thin film solar cells
  • Increases charge collection efficiency

  • Professor Lionel Kimerling (Department of Materials Science and Engineering, MIT)
  • Kazumi Wada (Materials Processing Center, MIT)

Intellectual Property:

U.S. Patent Number 6,750,393, issued June 15, 2004



Last revised:November 8, 2010

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