Carrier dynamics in the potential-induced degradation in single-crystalline silicon photovoltaic modules

In this study, transient diffuse reflectance spectroscopy (TDRS) and electroluminescence (EL) analysis have been employed to clarify the carrier dynamics in potential-induced degradation (PID) in single-crystalline Si (sc-Si) solar cell. We first localized the PID-affected region in terms of degradation intensity on the modules on the basis of EL. The carrier dynamics in that region are then studied and clarified in terms of carrier lifetime, defect level, and photogenerated carrier density. Our results suggest that carrier relaxation in a fresh solar cell proceeds via band to band and/or shallow and deep donor-acceptor recombination. However, the dominant recombination in solar cells with PID is intercenter charge transfer via shallow-to-deep and/or deep-deep defects for which the carrier lifetime decreased drastically. Also, it is found that the carrier dynamics near the surface and bulk do not progress similarly as confirmed using 532- and 1064-nm-wavelength pumps. (c) 2018 The Japan Society of Applied Physics.