Bandgap imaging in Cu(In,Ga)Se₂photovoltaic modules by electroluminescence

Abstract

A unique non‐destructive characterization method for apparent bandgap imaging in photovoltaic (PV) devices based on acquisition of two electroluminescence (EL) images in different spectral ranges is presented. The method consists of a calibration procedure and a bandgap imaging procedure. Calibration has to be performed once per module type and EL imaging setup, and must provide a relation between the bandgap and the ratio between two spectrally independent EL images. After calibration, bandgap imaging only requires acquisition of two spectrally independent EL images followed by image processing, making the method very fast and suitable for in‐line PV module characterization with regard to spatial (in)homogeneity and production process stability. The method is demonstrated on a commercial state‐of‐the‐art Cu(In,Ga)Se2 PV module where apparent bandgap fluctuations between 1.07 and 1.15 eV are detected. Copyright © 2016 John Wiley & Sons, Ltd.