Photovoltaic (PV) encapsulant film is a critical material in the encapsulation process of PV modules and is one of the constituent materials of PV modules. The film bonds PV cells, glass, and backsheet, primarily protecting the cells and encapsulating them into modules that generate DC power. Since the anti-PID* performance of PV modules directly affects the working efficiency and lifespan of solar panels—i.e., higher PID* leads to greater performance degradation—testing the anti-PID performance of encapsulant films has become a very important part of film R&D.

How to evaluate the anti-PID performance of PV modules?
Because encapsulant films with different molecular structures exhibit different volume resistivity and water vapor transmission rates under the same environment. A higher volume resistivity of the film corresponds to a lower water vapor transmission rate and a lower absolute leakage current. Therefore, the anti-PID performance of the encapsulant film can be characterized indirectly by measuring its volume resistivity.

Relevant standard
According to the test requirements in IEC 62788-1-2, sections 5.3.2 and 5.4.2, the volume resistivity test method for encapsulant films requires a test voltage of (1000 ± 5) V and a test duration of 60 seconds.