Effects of passivation configuration and emitter surface doping concentration on polarization-type potential-induced degradation in n-type crystalline-silicon photovoltaic modules

System voltages can cause significant degradation in photovoltaic modules. Polarization-type potential-induced degradation (PID) is accompanied by decreases in the short-circuit current density and the open-circuit voltage. The system voltage causes a polarization and surface charge accumulation, increasing the interface recombination. The surface passivation and the emitter doping concentration and gradient are considered to have large impacts. However, a systematic study on these effects has not yet been performed. In this paper, the effects of the front surface structure of n-type passivated emitter and rear totally diffused cell modules were investigated by accelerated PID tests. Standard cells with thin silicon dioxide/80-nm silicon nitride (SiNx) antireflection/passivation layers, refractive index (RI) of 2.0, exhibited typical polarization-type PID. Cells with increased RI = 2.4 for the bottom 20-nm SiNx showed no degradation at all. This may be caused by reduced charge accumulation in the SiNx layer near the interface due to the higher electrical conductivity of the Si-rich bottom layer. Secondly, cells with both a highly distorted interface, due to nitrogen insertion in the silicon surface, and an emitter with a high surface doping concentration have excellent resistance to PID. Cells with either the highly distorted interface or the higher emitter-surface doping concentration show no to minor improved resistance to PID. These findings improve the understanding of the effects of the front surface structure of cells on the polarization-type PID and may contribute to the implementation of these measures to reduce PID. •This study focused on the effects of the surface passivation configuration and the emitter-surface doping concentration of front-emitter, n-type crystalline silicon photovoltaic modules on their potential-induced degradation.•Cells with stacked SiNx layers composed of a 60-nm top layer with a refractive index of 2.0 and a 20-nm interlayer with refractive index of 2.4 showed no degradation.•Cells with both a distorted interface and surface-etched emitter that has a high surface doping concentration were confirmed to exhibit excellent resistance to potential-induced degradation.•These findings improve the understanding of polarization-type PID and contribute to the implementation of these measures to prevent the PID.