The prospective efficiency improvements due to advanced metallisation technology of industrially fabricated Czochralski (Cz) silicon solar cells are assessed by means of highly predictive numerical modelling in two- and three dimensions. The analysis shows that an improved emitter design is only possible with advanced metallisation concepts, and that about 19% efficiency can be achieved with this. Then, the fully metallised back surface field (BSF) limits cell performance. If this BSF is replaced by point contacts without substantial BSF (PERC design), the efficiency is limited to about 20% because the wafer resistivity must be 0.5 Ωcm at maximum, so Cz material has a very limited carrier lifetime due to the boron-oxygen complex. If local BSFs are formed at the rear point contacts (PERL design), higher wafer resistivities can be used, so the base operates under high-injection conditions where the boron-oxygen complex is less detrimental. However, such improvements to the rear side increase cell efficiency only substantially if the lifetime in the Cz material, in particular its interstitial oxygen density, is reduced.