Among the many characterization techniques for solar panel testing, two, electroluminescence
(EL) and photoluminescence (PL), can provide useful visual information
about the presence of different types of cell defects. EL is performed outdoors
by night in commercial solar plants due to the very weak luminescence emission
compared to sunlight. PL faces the added difficulty of needing to find a large-area
homogeneous light source to excite the modules. Since nighttime work poses many
drawbacks and risks, a daylight outdoor EL/PL system would be useful for offering
safe inspection of solar plants. We present daylight luminescence techniques
based on a bias switching method, in which a pulsed luminescence signal is obtained
by alternating the polarization state of the solar panels, synchronizing it with the
luminescence image detection by an InGaAs camera. Fast switching and selecting
an optimized exposure time are key to achieving high-quality images. The daylight
luminescence method described herein allows both EL and PL luminescence images
to be obtained, even under high solar irradiance conditions.
