Influence of heating profiles on crack inspection in polysilicon photovoltaic cells using electronic speckle pattern interferometry

• Main Author: 李劭遠
• Other Authors: 尹慶中
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/82039788173281635806

碩士 === 國立交通大學 === 機械工程系所 === 101 === The 6-inch polysilicon wafers for use of photovoltaic (PV) cells are thin enough, and possess both flexibility and brittleness. The latent defects which could not be found in PV cells by the unaided eye in the production line usually result in efficiency reduction and damage of solar panel. It remains an important issue to eliminate defective products before module process or end applications. Solar cell is a laminate structure mainly composed of silicon and porous aluminum. Thermal mismatch usually causes a bow of the cell exerted by temperature variation. This study numerically explores eight types of heat flux patterns and their influences on transient thermal deformation of the PV cell by the finite element method (FEM). The out-of-plane thermal deformation measurements were carried out by electronic speckle pattern interferometry (ESPI) with the suitable heat flux patterns that can induce clear fringes for identification of crack. Both the contour of out-of-plane displacement calculated by FEM and speckle fringe patterns detected by ESPI reveal the obvious changes near cracks due to heating profile gradually decreasing from periphery inwards. However, the crack initiated at one-quarter periphery off the center of edge can be only detected by use of unsymmetrical and long stripe-like heating profiles. Speckle patterns for surface cracks at the edge of cells appear with chevron-shaped fringes. Broken fringes are found for the through-cracks. The outcome of this study can be implemented as a real-time, whole field, nondestructive testing system for detection of surface cracks and through cracks in PV cells in the production line. Keywords: Crack detection, electronic speckle pattern interferometry, polysilicon photovoltaic cells, thermal deformation