Comparison of potential-induced degradation (PID) of n-type and p-type silicon solar cells

Abstract

Potential-induced degradation (PID) of photovoltaic (PV) modules is one of the most severe types of degradation, where power losses on system level may even exceed 30%. The PID process depends on the strength of the electric field, the temperature, the relative humidity, conductive soiling, time and the PV module materials. For p-type cells, it has been established that the decrease of the shunt resistance, due to migration of sodium ions across the n/p junction is the root cause of the degradation. On the other hand, it has recently been confirmed for n-type cells that the PID occurs due to an increase in recombination as charges are driven to the anti-reflection (AR) coating/emitter interface. In this paper, we present the comparison between PID of p-type and n-type crystalline silicon (c-Si) solar cells and their progression of PID. The time evolution of PID is studied by light and dark I-V curve measurements, electroluminescence images and progressions of the one- and two-diode equivalent model parameters, viz. photocurrent, 1st and 2nd diode reverse saturation currents, 1st and 2nd diode ideality factors, shunt resistance and series resistance.