Reduction in the short-circuit current density of silicon heterojunction photovoltaic modules subjected to potential-induced degradation tests

•SHJ PV modules undergo PID characterized by a reduction in short-circuit current.•The reduction is due to optical loss that probably occurs in the front TCO layer.•SHJ PV modules have high PID resistance.•The high reliability can be further improved by using ionomer encapsulants.

This letter deals with the potential-induced degradation (PID) of silicon heterojunction (SHJ) photovoltaic (PV) modules. After rapid indoor PID tests applying a voltage of −1000 V at 85 °C, the modules exhibited a significant reduction in short-circuit current density (Jsc). On the other hand, the dark current density-voltage characteristics of the modules were intact after the PID tests, indicating that the reduction in Jsc is attributed not to carrier recombination but to optical loss. A degraded module slightly recovered its performance loss upon applying a positive bias but complete recovery was not observed, showing that the PID of SHJ PV modules is not reversible. A module with an ionomer encapsulant showed high PID resistance, revealing that the degradation of SHJ PV modules can be prevented by the use of ionomer encapsulants.