A review of imaging methods for detection of photoluminescence in field-installed photovoltaic modules

Contactless detection with a camera of radiation emitted from silicon solar cells resulting from band-to-band recombination after charge carrier excitation with an illumination source, i.e. photoluminescence (PL) imaging, has shown a great potential in the laboratory setting. In the recent years, the first approaches to PL imaging in the outdoor setting have been conducted on silicon modules with the Sun, a LED module and laser as excitation sources. The reason for these attempts has been that fault detection in photovoltaic (PV) modules using imaging can be more efficient and accurate than fault detection using electrical parameters. Developments in fault detection and localization are necessary because accurate monitoring of solar plants is expected to be one of the critical tasks facing the energy industry, when one considers that PV energy conversion will be the largest installed power capacity by 2027 and that the utility-scale solar PV electricity generation will be the least costly option for new electricity generation in many of the world’s countries. The present study sums up the different methods for outdoor PL imaging and emphasizes their differences regarding filtering of the reflected excitation light from the PL signal. The different types of PL images obtained from each method and the image processing algorithms are described. Finally, the interpretation of the different types of PL images is addressed.