The effect and mechanism of current injection to suppress light and elevated temperature induced degradation in p-type cast-mono and multicrystalline silicon Passivated Emitter and Rear cells

In this work, we demonstrate that the forward current injection together with annealing as pre-treatment can dramatically suppress V-oc degradation in both p-type Cast-Mono silicon (CM-Si) and multicrystalline silicon (mc-Si) Passivated Emitter and Rear Cells (PERC) during the following prolonged Light and elevated Temperature Induced Degradation (LeTID) stability test. To explore the underlying mechanisms, the dependence of the suppression extent of the V-oc degradation upon applied currents and temperatures is studied. Interestingly, it is found that the modest injected current and annealing temperature are best for cell performance, leading to an evident increase (up to 0.4 %rel) in V-oc as well as the degradation extent during LeTID stability test can be minimized to only 0.2 %(rel) and 0.4 %(rel) for CM-Si and mc-Si PERC, respectively. This result is based on large number of commercial cells and therefore shows huge potential for application into mass production and may be of significance to the global photovoltaic industry. Finally, a qualitative model based on the different states and behaviors of the potential participants hydrogen, is proposed to explain the underlying mechanisms of LeTID and anti-LeTID behaviors in CM-Si and mc-Si.

Automated summary

This work demonstrates that forward current injection and annealing pre-treatment can significantly suppress V-oc degradation in both p-type Cast-Mono silicon and multicrystalline silicon Passivated Emitter and Rear Cells (PERC) during prolonged Light and elevated Temperature Induced Degradation (LeTID) stability test. The study also reveals that modest injected current and annealing temperature are optimal for cell performance.