Investigation of polysilicon passivated contact's resilience to potential-induced degradation

We present clear evidence of excellent resilience to potential-induced degradation (HD) from polysilicon passivated contacts implemented on the rear of n-type solar cells. Under the stress conditions of -1000 V, 50 degrees C, 30% relative humidity with aluminum foil, no damage was caused to the passivated contact consisting of an ultrathin silicon oxide (SiOx) film and an n(+) doped polysilicon (poly-Si) layer after 168 h. With + 1000 V bias and under the same chamber conditions, the SiOx/poly-Si (n(+)) passivated contact showed a slight change that translated into about 1% module power loss after 168 h, which is significantly lower than the 5% threshold recommended by IEC 62804.1 PID test standard. Furthermore, the SiOx/poly-Si (n(+)) passivated contact, even when encapsulated with ethylene-vinyl acetate copolymer films having a low volume resistivity in the range of 5 x 10(14) Omega.cm, exhibited good stability under high-voltage stress. The experimental results were also validated by a generic device simulation, where the SiOx/poly-Si (n(+)) stack was shown to be immune to the surface polarization effect. In addition, a promising cell-level solution (i.e., using a stack of aluminium oxide and silicon nitride) to the polarization-type PM for n-type passivated emitter rear totally diffused silicon solar cells was also demonstrated.