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 SiN
_x
, level of Na contamination, and segregation kinetics of Na in SiN
_x
. Based on a sensitivity analysis on the expected electric field and levels of Na contamination at the surface of SiN
_x
, we identify a relationship between the diffusivity of Na in the stacking faults present in the emitter and the kinetics of shunt resistance,
$R_{\mathrm{sh}}$
. 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 SiN
_x
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.