Correlations of photo-electro-thermal-luminescent imaging of Cu(In,Ga)Se2 with device performance, defects, and micro-structural properties

Several camera imaging techniques have been applied to the characterization of Cu(In,Ga)Se₂ (CIGS) solar cells having a range of efficiencies. Photoluminescence (PL) imaging shows brightness variations after the deposition of the CIGS layer that persist through CdS deposition and subsequent processing steps to finish the devices. PL and electroluminescence imaging on finished cells show a correlation to the devices´ corresponding efficiency and open-circuit voltage (VOC), and dark defect-related spots correspond to bright spots on images from illuminated lock-in thermography (LIT) and forward-bias dark LIT. These image-detected defect areas are weak diodes and shunts. Imaging provides locations of defects detrimental to solar cell performance. Some of these defects are analyzed in more detail by scanning electron microscopy techniques using top and cross-sectional views.