Optical absorption enhancement in amorphous silicon nanowire and nanocone arrays

Nano Lett. 2009 Jan;9(1):279-82. doi: 10.1021/nl802886y.

Abstract

Hydrogenated amorphous Si (a-Si:H) is an important solar cell material. Here we demonstrate the fabrication of a-Si:H nanowires (NWs) and nanocones (NCs), using an easily scalable and IC-compatible process. We also investigate the optical properties of these nanostructures. These a-Si:H nanostructures display greatly enhanced absorption over a large range of wavelengths and angles of incidence, due to suppressed reflection. The enhancement effect is particularly strong for a-Si:H NC arrays, which provide nearly perfect impedance matching between a-Si:H and air through a gradual reduction of the effective refractive index. More than 90% of light is absorbed at angles of incidence up to 60 degrees for a-Si:H NC arrays, which is significantly better than NW arrays (70%) and thin films (45%). In addition, the absorption of NC arrays is 88% at the band gap edge of a-Si:H, which is much higher than NW arrays (70%) and thin films (53%). Our experimental data agree very well with simulation. The a-Si:H nanocones function as both absorber and antireflection layers, which offer a promising approach to enhance the solar cell energy conversion efficiency.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Crystallization / methods*
  • Light
  • Macromolecular Substances / chemistry
  • Materials Testing
  • Molecular Conformation
  • Nanostructures / chemistry*
  • Nanostructures / ultrastructure*
  • Nanotechnology / methods*
  • Particle Size
  • Refractometry
  • Scattering, Radiation
  • Silicon / chemistry*
  • Surface Properties

Substances

  • Macromolecular Substances
  • Silicon