Electroluminescence (EL) is an optical phenomenon and electrical phenomenon in which a material emits light in response to the passage of an electric current or to a strong electric field. One example of EL is that when current passes through solar photovoltaic (PV) cells light emission occurs. Testing of modules using this phenomenon can detect hidden defects in the structure of PV cells, e.g. cracks, broken cells, interconnections and shunts, etc. This method makes the current distribution visible in the PV module and helps detect defects.
Drones are a beneficial tool for solar panel inspections, particularly those with a EL payload using EL imaging technique are powerful in detecting hidden defects, which thermal or RGB imaging can rarely detect.