Optical absorption enhancement in amorphous silicon nanowire and nanocone arrays.
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.
Zhu
Jia
J
Department of Electrical Engineering, Department of Applied Physics, Department of Materials Science and Engineering, and Department of Chemistry, Stanford University, Stanford, California 94305, USA.
Yu
Zongfu
Z
Burkhard
George F
GF
Hsu
Ching-Mei
CM
Connor
Stephen T
ST
Xu
Yueqin
Y
Wang
Qi
Q
McGehee
Michael
M
Fan
Shanhui
S
Cui
Yi
Y
D003460:Crystallization / Q000379:methods*; D008027:Light; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D036103:Nanotechnology / Q000379:methods*; D010316:Particle Size; D012031:Refractometry; D012542:Scattering, Radiation; D012825:Silicon / Q000737:chemistry*; D013499:Surface Properties
D046911:Macromolecular Substances; D012825:Silicon