Recombination in passivating contacts: Investigation into the impact of the contact work function on the obtained passivation

Improving the passivation of contacts in silicon (Si) solar cells is crucial for reaching high-efficiency devices. In this study, the impact of the contact work function on the obtained passivation is examined and quantified using a novel method—quasi-steady-state photoluminescence—which provides access to the surface saturation current density after metallisation (J0s,m). The obtained J0s,m indicates an improvement of the surface passivation when contacts with high work function are applied onto Si wafers passivated with aluminium oxide, regardless of the wafer doping type. This improvement is mainly due to the amplification of the imbalance between the electron and hole concentrations near the Si interface. The passivation quality is reduced when using contacts with low work function in which the recombination rate increases via the charge-assisted carrier population control. This study points to the vital importance of selecting suitable metals to minimise contact recombination in high-efficiency solar cells.