Activation Energy of PID-p Degradation for Bifacial p-PERC Silicon Minimodules

The activation energy determination for polarization type potential-induced degradation (PID-p) was conducted on bifacial, single-cell, double-glass minimodules. The minimodules were fabricated with two types of monocrystalline p-PERC solar cells produced by two cell manufacturers (CT1 and CT2). In both module types, EVA was used as the rear encapsulant, promoting PID-p progression in the rear passivation stack, while POE was used as the front encapsulant. Mono-facial PID tests, i.e., front- side PID test and rear-side PID test arrangement were separately used at three temperatures (25<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sup>C, 45<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sup>C and 60<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sup>C; one minimodule per side per temperature leading to six test modules per cell type) for 168 hours using the metallic foil method at 54% relative humidity (RH) and -1500 V applied voltage to the solar cells. Both CT1 and CT2 minimodules showed PID-p susceptibility on the rear side as indicated by the short-circuit current (I<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SC</inf>) reduction and PID-s resistance on the front side as indicated by the insignificant impact on fill factor (FF). The activation energies determined using the average magnitude of steady-state leakage current were: 0.46 eV for CT1 minimodules and 0.60 eV of CT2 minimodules when stressing cell’s rear. The impacts of the negative voltage PID stress and encapsulant type (POE vs. EVA) on performance parameters for the front-side and rear-side of these bifacial minimodules are also provided and explained.