Full wafer size IBC cell with polysilicon passivating contacts

Abstract

We investigate the application of polysilicon carrier-selective passivating contacts to IBC cells. We optimized the passivation of n-type and p-type polysilicon layers by managing the hydrogen supply to the interfacial oxide. Both surface passivation and firing stability were addressed. The best results so far are obtained for passivation capping layers that contain Al2O3 and SiNx. For these passivated polysilicon layers, we present excellent J0 and implied Voc values on textured n-Cz wafers, with best values of < 1 fA/cm2 and 741 mV for n-type, and 10 fA/cm2 and 720 mV for p-type polysilicon, which are maintained after firing. The polysilicon layers were applied as carrier-selective passivating contacts for a full wafer size (156×156 mm2) IBC cell, using industrial compatible processes and commercially available n−type Cz wafers. The implied Voc on the cell reaches 725 mV, which enables IBC cell efficiencies of 24%. After metallization, Voc values of close to 700 mV were obtained.