Contactless Outdoor Photoluminescence of Silicon Photovoltaic Modules with Large Area Excitation Source

Cost-effective tools for on-site defect detection help to ensure the reliable power production of photovoltaic (PV) plants. On-site examination is essential to minimize PV module damage, electrical yield loss and operation disruption caused by additional transport to the laboratory (off-site examination) or disruption of the electrical circuits. Outdoor inspection may be carried out by using highly sensitive imaging techniques, such as luminescence or thermography imaging. To avoid electrical contact switching time for electroluminescence (EL), we replaced intrusive electrical excitation by non-contact excitation with light, and measured photoluminescence (PL) instead. Nowadays, luminescence is used to detect defects such as increased series resistance, local cell irregularities, shunts and electrical disconnections in solar cells and modules. Our excitation source consists of twelve broadband, white, high power (100 W electrical power), chip on board light emitting diodes (LEDs) coupled with low-cost short pass filters. The light source is suitable for InGaAs and silicon (Si) detectors and mobile outdoor applications, which makes this setup a tool for on-site PL inspections for large area modules. The PL setup presented in this paper is capable of measuring large area PV modules of up to 72 cells with one image