Light Trapping in Nanostructured Black Semiconductors

• Main Authors: Srikanth Ravipati, 阮士康
• Other Authors: Ko, Fu-Hsiang
• Format: Others
• Language: en_US
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/47031213739704430710

博士 === 國立交通大學 === 材料科學與工程學系奈米科技碩博士班 === 101 === Light trapping is very essential for solar cells to enable its efficient performance. Developing sub-wavelength nanostructures to efficiently absorb the light is an attractive method to avoid large reflection losses from any semiconductor material. Fabrication of nanostructured materials with super blackness is one of the cornerstones of present photovoltaic research. Although few super black materials have been proven with near zero reflection and near unity absorption, semiconductor based black materials has become an increasingly important black material for solar cell applications. Furthermore, semiconductor based black materials can be fabricated along with current solar cells technology. In this thesis we explore the fabrication and light trapping properties of nanostructured black semiconductors. The overview of potentiality of our hydrogen plasma etching process to fabricate wide variety of nanostructures including semiconductors and dielectrics is presented. In the first part, we fabricate randomly textured poly-Si and a-Si nanostructures from pre-deposited one micron thin films. We show the unique double layered nanostructures of a-Si nanograss on top of Si nanofrustum behaves as most similar to a black material. In the second part, we demonstrate that the hydrogen plasma etching process can be extended to fabricate grass like GaAs nanostructures. Antireflection performance of almost independent of polarization of the incident light over a broad range of wavelengths and wide range of incidence angle from GaAs nanograss is revealed. In the final part, we explore the fabrication of flexible ultrathin crystalline silicon films by wet chemical etching. We also extended the fabrication of nanograss-like structures on flexible ultrathin crystalline silicon films, using hydrogen plasma etching process. The combination of high optical absorption and extremely low reflectance of the nanostructured ultrathin crystalline silicon films over a broad range of wavelengths from 300 to 800 nm demonstrates its super blackness.