Performance evaluation of multi-junction solar cells by spatially resolved electroluminescence microscopy

An electroluminescence microscopy combined with a spectroscopy was developed to visually analyze multi-junction solar cells. Triple-junction solar cells with different conversion efficiencies were characterized by using this system. The results showed that the mechanical damages and material defects in solar cells can be clearly distinguished, indicating a high-resolution imaging. The external quantum efficiency (EQE) measurements demonstrated that different types of defects or damages impacted cell performance in various degrees and the electric leakage mostly degraded the EQE. Meanwhile, we analyzed the relationship between electroluminescence intensity and short-circuit current density J(SC). The results indicated that the gray value of the electroluminescence image corresponding to the intensity was almost proportional to J(SC). This technology provides a potential way to evaluate the current matching status of multi-junction solar cells.