Polarization-Type Potential-Induced Degradation in Front-Emitter p-Type and n-Type Crystalline Silicon Solar Cells

For SiO₂ layers underneath the SiN antireflection/passivation layers of front-emitter p-type c-Si solar cells, this paper presents an investigation into their effects on polarization-type potential-induced degradation (PID), in addition to a comparison of polarization-type PID behavior in front-emitter p-type c-Si cells and front-emitter n-type c-Si cells. After PID tests with a bias of +1000 V, p-type c-Si cells without SiO₂ layers underneath the SiN layers showed no degradation, although p-type c-Si cells with approx. 10 nm thick SiO₂ layers showed polarization-type PID, which is characterized by a reduction of the short-circuit current density and the open-circuit voltage. This result implies that highly insulating layers such as SiO₂ layers play an important role in the occurrence of polarization-type PID. Comparison of polarization-type PID in p-type and n-type c-Si cells with SiO₂ layers indicated that degradation in the n-type cells is greater and saturates in a shorter time than in the p-type cells. This result is consistent with an earlier proposed model based on the assumption that polarization-type PID is caused by charge accumulation at K centers in SiN layers. The findings described herein are crucially important for elucidating polarization-type PID and verifying the degradation model.