The Investigation of Silicon Nanostructures for Optoelectronic Devices

• Main Authors: Ying-kan Yang, 楊穎侃
• Other Authors: Bohr-ran Huang
• Format: Others
• Language: en_US
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/33427304371949196746

博士 === 國立臺灣科技大學 === 電子工程系 === 102 === This study presents a simple approach and cost-effective techniques to develop the silicon nanostructure (SNS) based high performance optoelectronic devices. The SNS provide a number of combined properties including excellent electronic/optical properties, favorable biocompatibility, huge surface-to-volume ratios, and excellent anti-reflection property. The SNS offer good performance in applications for field emission (FE) devices, gas sensors, and solar cells. The CNTs grown directly onto the SiNRs forming a core-shell structure of SiNRs/CNTs field emission cathode by thermal chemical vapor deposition. The field emission properties of SiNRs, CNTs and SiNRs/CNTs field emission cathodes were investigated. It is exhibited that this core-shell structure of SiNRs/CNTs for field emission cathode improves the field emission properties. The metal-assisted electroless etching (MAEE) and repeated MAEE techniques of fabricating straight-aligned and rice-straw-like SiNW arrays for hydrogen gas sensing. The rice-straw-like SiNW arrays structure effectively increased the surface area and the concentration of silicon oxide, which provided additional binding sites for gas molecules. A cost-efficient method to texture monocrystalline silicon by depositing a layer of Si3N4 by sputtering to act as an anisotropic etching mask. Anisotropic etching through this mask forms various pyramid structures depending on the thickness of the Si3N4 layer. The texturing process is evaluated in terms of the resulting surface morphology and the reflectivity. The low cost MAEE, PSG dopant solution and a screen-printing technique are adopted to fabricate the n+ emitter and the electrodes for silicon nanowire (SiNW) array based solar cells. Results indicate that there is a competition phenomenon between the aspect ratio and the density, that straight-aligned SiNW array structures with a certain aspect ratio and an appropriate density possesses better solar cell performance (~10.15%). Solar cells based on a high efficiency silicon nanostructure (SNS) are developed using the two step MAEE technique. Compared to cells produced using the single MAEE technique, SNS-based solar cells produced with the two step MAEE technique showed an increased silicon surface coverage of and a decrease in reflectivity. Performance of the SNS-based solar cell is found to be optimized (~11.86%) in SNS with a length of ~300nm, an aspect ratio of ~5, and surface coverage of ~84.9%. Moreover, the performance of the SNS-based solar cells is further to 13.29% by using the thermal oxidation passivation method. The SNS are successful synthesized by the facile methods and low manufacturing temperatures. This work proposes an effective way to enhance the performance of SNS based optoelectronic devices. The development of SNS in this thesis will be useful for the base of next-generation devices.