Transient carrier recombination dynamics in potential-induced degradation p-type single-crystalline Si photovoltaic modules

In this study, we investigated the recombination dynamics of minority carriers through the decay profile analysis of transient diffuse reflectance spectroscopy (TDRS) for fresh and potential-induced degradation (PID) modules. The PID-affected region in terms of the degradation degree on the modules was firstly localized using conventional methods such as electroluminescence (EL) and lock-in thermal images. The photogenerated carrier density and carrier lifetime were different in photovoltaic (PV) modules in fresh and PID modes. It was found that the dominant recombination involved the carrier transition via shallow trap states. The distribution of the trap states, however, was extended from the surface to the bulk of the solar cell due to Na ions-decorated defects. The behaviors of the carrier dynamics near the surface and bulk were very different, as inferred from the two different pump wavelengths of 532 and 1064 nm, respectively.