Quantitative analysis of relationship between leakage current and power loss of multi-crystalline silicon photovoltaic module during potential-induced degradation test

Abstract

The relationship between the leakage current and the power loss of a multi-crystalline silicon photovoltaic module during potential-induced degradation (PID) tests was analyzed. Since the current flowing into cells through a cover glass and an ethylene–vinyl acetate encapsulant is highly related to Na+ ion migration, which is presumed to be the main cause of PID, a setup for accurately measuring the current was designed. PID tests were also conducted under different temperature and voltage conditions following the same setup. From the current measured during PID tests, the charge transferred onto the active cell area was estimated. It was found that there is a one-to-one relationship between the charge transferred onto the active cell area and the power loss of a module. This result suggests that the PID power loss is due to the amount of Na+ ions accumulated on the active cell area.