Potential-Induced Degradation of Bifacial PERC Solar Cells Under Illumination

Bifacial passivated emitter and rear cell (PERC) solar cells are promising candidates to reduce levelized cost of electricity since a rear-side power gain can be achieved with minor changes in cell production. However, in addition to the potential-induced degradation of the shunting type (PID-s), some bifacial solar cells may exhibit another degradation related to their rear side. Using three types of purchased industrial bifacial PERC cells encapsulated in our laboratory, we show that a rear-side PID test under simultaneous illumination can cause up to 14% power degradation, which is related to increased carrier recombination at the rear side of the cell. Thus, we find that the degradation under realistic field conditions is strong enough to significantly reduce the bifaciality gains. This is of particular importance as only some of the investigated cells recover under dark conditions. Microstructural analysis of the PID-stressed rear side reveals localized permanent structural damages of the passivation layer leading to an increased rear-side recombination.