A scanning nonlinear dielectric microscopic investigation of potential-induced degradation in monocrystalline silicon solar cells

Abstract

Carrier distributions in monocrystalline silicon solar cells affected by potential-induced degradation (PID) were investigated using scanning nonlinear dielectric microscopy (SNDM), employing three samples with different PID levels. These observations clearly demonstrated that reductions in the carrier density were correlated with the extent of PID. Depth profile measurements showed that the solar cells were affected by PID to a significant depth of approximately 90 μm, equal to almost half the cell thickness. This result suggests that the Na+ migration is readily induced by the application of a high voltage. Super-higher-order-SNDM was also employed to obtain a more precise analysis of the depletion layer distributions in monocrystalline silicon solar cells with and without the application of a high voltage. The data showed that the depletion layer of a sample without PID was thinner than that of a sample exhibiting PID, indicating that the carrier concentration in the former sample was higher. This finding was in good agreement with the results produced by direct quantitative dopant measurements using SNDM.