Preparation and Study of Oxidized Nano-Porous-Si (ONPS) Thin-Films for Applications of Photo-Voltaic Devices

• Main Authors: Feng Wei Huang, 黃峯偉
• Other Authors: Kuen Hsien Wu
• Format: Others
• Language: zh-TW
• Published: 100
• Online Access: http://ndltd.ncl.edu.tw/handle/82033894924740548085

碩士 === 南台科技大學 === 光電工程系 === 99 === Due to its relatively small optical bandgap (<2.0eV), the optical-absorption ability of the Nano-Porous-Silicon (NPS) prepared from an electrochemical etching technology is quite poor for ultra-violet (UV) light. In this thesis, we proposed Oxidized Nano-Porous-Si (ONPS) thin-films that were developed from NPS films by rapid-thermal-oxidation (RTO) methods for serving as the light-absorption layers of photovoltaic devices to increase the absorption efficiency of short-wavelength light. In addition, we used the developed ONPS films combined with multi-layered PS (MLPS) structures to achieve a broader wavelength range of light-absorption to enhance the conversion efficiency of PS photo-voltaic devices. Firstly, NPS thin-films with uniformly distributed Si nano-crystallites were prepared on heavily doped n+-type (100) Si wafers (1~3 m-cm) by anodic etching processes. Then ONPS thin-films were obtained from NPS by RTO treatments, in which different oxidation time was used to modulate the physical structures and optical absorption properties of ONPS films. Finally, photo-voltaic devices were made with ONPS films combined with MLPS structures as the light-absorption layers, after depositing inter-digitated aluminum (Al) electrodes on the front sides of the devices. EDS and XPS analysis showed that the atomic ratio of oxygen to silicon in the developed NPS films had significantly varied and the strength of the binding energy of SiOx at 103.3eV also increased after oxidation processes, indicating NPS films had partially converted into ONPS films. Photo-response spectrum analysis illustrated that ONPS thin-films could effectively absorbed UV light of wavelength within 300~400nm and MLPS photo-voltaic devices could obtain broader light-absorption wavelength range (300~900nm) than those of single-layered NPS devices. It had found form Solar-Simulator measurement that the conversion efficiency of devices with ONPS-imbedded MLPS structures is much higher than that of single-layered NPS devices. It was thought that the improvement of conversion efficiency was owing to the broader light-absorption spectra, as a result of the design of MLPS structures and the addition of ONPS layers.