Dielectric Charge Tailoring in PECVD SiO /SiN Stacks and Application at the Rear of Al Local Back

State-of-the-art surface passivation results are obtained on undiffused p-type commercial-grade Czochralski Si wafers with effective surface recombination velocity S_eff values of ~8 cm/s and implied open-circuit voltage iV_oc values of up to 715 mV with an industrially fired dielectric stack of silicon oxide and silicon nitride (SiO_x/SiN_x) deposited in an industrial inline plasma-enhanced chemical vapor deposition reactor. We are able to controllably vary the total positive charge density Q_total in the stack by more than one order of magnitude (10¹¹-10¹² cm^-2) with no impact on midgap interface state density D_{it,m idgap} (5 × 10¹¹ eV^-1· cm^-2) by altering the deposition temperature of the SiO_x layer in the stack. We show experimentally that, for inversion conditions, S_eff scales with the inverse square of the charge density 1/Q²_total, which is in good agreement with theory. Based on the measured injection-level-dependent minority carrier lifetimes and the total positive charge densities, it is shown that films with higher positive charge density have higher 1-sun Voc and fill factor (FF) potential. Large-area alloyed aluminum local back surface field solar cells confirmed this by showing higher conversion efficiency by 0.17% absolute due to improved cell V_oc and FF of the solar cells featuring a SiO_x/SiN_x stack with a higher Q_total.