Finite Element Simulation of Potential-Induced Degradation Kinetics in p-Type Silicon Solar Modules

We present a physics-based model to describe the kinetics of potential-induced degradation (PID) in p-Si photovoltaic (PV) modules, parametrized by the diffusivities of Na in the module stack, electric field in the SiNx, level of Na contamination, and segregation kinetics of Na in SiNx. Based on a sensitivity analysis on the expected electric field and levels of Na contamination at the surface of SiNx, we identify a relationship between the diffusivity of Na in the stacking faults present in the emitter and the kinetics of shunt resistance, R sh. These findings indicate a faster diffusion mechanism through the stacking faults than that which would be expected for bulk Si, for PID-prone p-Si modules. Our simulations imply that a decrease in the SiNx resistivity alone cannot explain robustness to PID-s, suggesting that a diffusivity dependence on the nitride chemistry may be responsible in part for PID-robust devices. We show that additional interface engineering could potentially reduce the ingress of Na and hence PID by allowing Na to segregate on interface layers.