Application Note

Solar Cell Inspection

Solar cell inspection relies on imaging the photoluminescence or electroluminescence signals from a wafer to characterise it. The peak emission for Silicon occurs at about 1150nm while it is around 1330nm for Copper Indium Gallium di-Selenide (CIGS) and Copper Indi-um di-Selenide (CIS).

This value is out of the range of sensitivity for Silicon based detectors, such as CCDs, and traditionally their quantum efficiency is only measured up to 1000nm. However, the emission peak is actually broad enough to allow deep cooled CCD to capture meaningful images using very long integration times (typically minutes). Although interesting, this is insufficient and unpractical for industrial applications.

Alternatively, shortwave infrared (SWIR) InGaAs technology is ideal to directly detect the electroluminescence emitted at 1.3µm by solar cells and ensure their quick characte-rization (within milliseconds) either during manufacturing or for pre-emptive maintenance operation of a photovoltaic plan. 

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