Analtic Findings in the Photographic Characterization of Crystalline Silicon Solar Cells using Electroluminescence

The electroluminescence (EL) intensity from Si cells under the forward bias was found to have one to one quantitative agreement with the minority carrier diffusion length. Based on the diffusion equation, the EL intensity was analyzed relating to the cell performance. Diffusion length difference between grains could be elucidated in addition to the clear imaging of grain boundaries. When the effective diffusion length was influenced by the rear surface recombination velocity (i.e., the bulk diffusion length was longer than the active layer thickness), the EL intensity represented the quality of rear surface passivation processes. Ideality factor n could be deduced by measuring the EL intensity as a function of the forward injection current