Effect of a silicon nitride film on the potential-induced degradation of n-type front-emitter crystalline silicon photovoltaic modules

Abstract

We investigate the effect of silicon nitride (SiNx) films in n-type front-emitter (n-FE) crystalline Si (c-Si) solar cells on the potential-induced degradation (PID) of n-FE photovoltaic (PV) modules. A negative-bias PID test for a few min does not degrade the performance of PV modules with n-FE cells without SiNx/Si dioxide (SiO2) stacks, unlike in the case of PV modules with cells with SiNx/SiO2. This is because of the absence of polarization-type PID. After a longer PID test, the PV modules with n-FE cells without SiNx/SiO2 show a slower decrease in fill factor (FF), originating from Na introduction into the depletion layer of a p–n junction, than the modules with cells with SiNx/SiO2. The mitigation of PID by eliminating SiNx is partly consistent with the results of PV modules with p-type conventional cells without SiNx in which no PID occurs. SiNx thus has a function of enhancing Na introduction into c-Si.