Defect recognition by means of light and electron probe techniques for the characterization of mc-Si wafers and solar cells

Abstract

a b s t r a c tMulticristalline Silicon (mc-Si) is the preferred material for current terrestrial photovoltaic applications. However, the high density of defects present in mc-Si deteriorates the material properties, in particular the minority carrier diffusion length. For this reason, a large effort to characterize the mc-Si material is demanded, aiming to visualize the defective areas and to quantify the type of defects, density and its origin. In this work, several complementary light and electron probe techniques are used for the analysis of both mc-Si wafers and solar cells. These techniques comprise both fast and whole-area detection techniques such as Photoluminescence imaging, and highly spatially resolved time consuming techniques, such as light and electron beam induced current techniques and mRaman spectroscopy. These techniques were applied to the characterization of different mc-Si wafers for solar cells, e.g. ribbon wafers, cast mc-Si as well as quasi-monocrystalline material, upgraded metallurgical mc-Si wafers, and finished solar cells.

Daylight luminescence system for silicon solar panels based on a bias switching method

“…EL consists of luminescence emission by solar cells under forward bias, 10 thereby spatially resolving defects that affect the performance and/or durability of the modules, such as cracks, heterogeneous cell activity, failed soldering, grid defects, and dark areas in cells associated with dislocation clusters 11‐18 . In contrast, PL consists of luminescence emission under excitation with light 19‐28 . The difficulty involved in obtaining a uniform large‐area light excitation source over the module surface has prevented it from being applied to module inspection.…”

Grain boundary light beam induced current: A characterization of bonded silicon wafers and polycrystalline silicon thin films for diffusion length extraction

“…While photoluminescence provides information about the radiative recombination activity, electron or light beam induced current (EBIC or LBIC) characterize the total recombination at localized defects . Both scanning techniques involve a locally focused beam reaching a high spatial resolution in sub‐micron range .…”