Spectral imaging aids PV production

With demand for photovoltaic (PV) panels more than doubling year on year, manufacturers are under increasing pressure to improve the efficiencies of the solar cells as well as their production yields.

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With demand for photovoltaic (PV) panels more than doubling year on year, manufacturers are under increasing pressure to improve theefficiencies of the solar cells as well as their production yields.

A joint team from the Department of Electrical and Computer Engineering at theNational University of Singapore and the Institute of Applied Physics at the University of Karlsruhe in Germany has demonstrated a novel imaging technique that could help.

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Based on the idea that some defective regions of a silicon-wafer solar cell show strong luminescence under reverse bias, Matthew Peloso and his colleagues have shown that by inducingelectroluminescence and then capturing images of the cells, the observed spectrum of emitted radiation can be used to identify particular performance-reducing defects.

In the experimental setup, solar cell images were captured by anAndor Technology (Belfast, Northern Ireland; www.andor.com) Luca-R EMCCD megapixel camera and a second Sinfrared (Singapore; www.sinfrared.com) 640 × 480-pixel indium gallium arsenide (InGaAs) camera to allow the detection of luminescence from 300–1700 nm.

The researchers say that detection of the changes in the emitted radiation can not only be used to understand the electrical properties of defects in the wafers but also to study their origin, which may lead to lower-cost, higher-quality materials for the production of solar cells.

They claim that the technique is also fast enough that it could be used in real-timein-line process monitoring, which could lead to higher average solar cell efficiency and improved yield in silicon-wafer solar cell manufacturing.

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