Process monitoring of multicrystalline silicon solar cells with quasi-steady state photoconductance measurements

Multicrystalline silicon (mc-Si) solar cell efficiency is strongly related to the bulk material lifetime due to the low electronic quality. The minority carrier lifetime of multicrystalline silicon can vary greatly during the high temperature furnace steps involved in cell processing. Quasi-steady state photoconductance (QssPc) measurements were used to monitor the lifetime of different mc-Si substrates and process sequences. It is important to identify the beneficial or detrimental processing steps, to minimise recombination (and therefore efficiency) at the completion of processing. The benefits of phosphorus diffusions and aluminium alloys were identified, while oxidation of ungettered substrates and metallisation contributed to increased recombination and decreased effective lifetimes