Potential-induced degradation of n-type front-emitter crystalline silicon photovoltaic modules - Comparison between indoor and outdoor test results

We perform indoor and outdoor potential-induced degradation (PID) tests for n-type front-emitter (n-FE) crystalline Si (c-Si) photovoltaic (PV) modules and compare their results. The indoor/outdoor acceleration factor for the polarization-type PID (PID-p) of n-FE PV modules is found to be similar to 1000 at an indoor test temperature of 85 degrees C. We observe the progression of the PID-p of n-FE PV modules in rainy days, while their performance is recovered in sunny days. This may be because of the formation of a water film on a module surface acting as a conductive film, resulting in a larger electric field near the n-FE cells in rainy days. The recovery of the PV performance of n-FE modules in sunny days can partly explain the large acceleration factor for the indoor PID test against the outdoor test.