Nanoscale Detection of Deep Levels in CIGS using Electron Energy Loss Spectroscopy

Correlation of electronic structure with nanoscale chemical and physical structure in photovoltaic (PV) materials can provide a pathway to improve fundamental understanding of the nature and impact of defects in solar cell devices. Recent advancements in scanning deep level transient spectroscopy (DLTS) have made it possible to better characterize defect distributions in CuInGaSe
₂
(CIGS) samples with both energy and surface lateral spatial resolution, but depth locations, as well as any information regarding chemical or structural features of the defective areas, are effectively unavailable with this technique. Here, scanning transmission electron microscope (STEM) based electron energy-loss spectroscopy (EELS) is employed toward a correlated analysis of the EV + 0.43 eV trap level. Preliminary STEM-EELS data reveals a 0.42 eV energy loss peak located within similar intergrain regions as indicated by scanning-DLTS, suggesting correlation and the potential for further targeted chemical and structural characterization.