A camera sold for infrared photography can also measure how well a solar cell works.

Researchers in Germany have shown that, with a filter and careful calibration, a commercially available camera can capture the faint light solar cells emit under an applied voltage and turn it into data about their quality.

The team from the University of Stuttgart, Research Center Jülich, and Solarzentrum Stuttgart conducted the research.

They aimed to make a quantitative measurement usually performed with a costly industrial camera using more accessible equipment.

When electricity is applied to a solar cell, it emits light in the infrared. This process, called electroluminescence, can reveal quality differences across a cell or module that would not be visible in an ordinary photograph.

Researchers use a measure called electroluminescent quantum efficiency to assess that emission. It is directly related to the cell’s voltage. In general, a higher value indicates a better-performing solar cell.

An image alone, however, does not provide a reliable efficiency measurement. The camera’s response to light must be understood and calibrated so that the brightness recorded in each part of the image can be translated into a quantitative result.

“An electroluminescence image contains much more quantitative information than simply showing bright and dark regions,” said Werner. 

“With a suitable physical camera model and calibration, it can provide absolute luminescent quantum efficiency and, therefore, information about the local quality of a solar cell or module,” he added.

The camera used in the study was already suited to infrared imaging because it lacked the internal infrared-blocking film found in most commercial cameras.

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