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 (1011–10 12 cm−2) with no impact on midgap interface state density D it,midgap (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 $1/Q_{{\rm total}}^2$ , 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 V oc 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.