Temperature dependence of polysilicon passivating contact and its device performance

The temperature coefficient (TC) of solar cells is an important figure of merit for any photovoltaic technology. Recently, tunnel oxide passivated contact (TOPCon) solar cells have attracted significant attention due to their potential to obtain high efficiency. Quantification of their TC is therefore of significant interest. In this study, we investigate (a) TCs of the TOPCon solar cells, and (b) the temperature dependence of polysilicon passivating contacts. For TOPCon cells using Czochralski-wafers, the relative TC of the cell efficiency is -0.285±0.005 %/°C. To our best knowledge, this is the first time that the efficiency TC of TOPCon cells is reported. This TC value is superior to those of devices without passivating contacts and is comparable to the one of silicon heterojunction cells. Using test samples, we observe an increase of the effective lifetime over the entire measured injection level range and a small improvement of the surface passivation quality when increasing the temperature. However, it seems these effects do not have a strong impact on the TC of the open-circuit voltage. We find that the improvement of the contact resistivity at elevated temperatures offsets some of the fill factor reduction and hence, improves the TC of the fill factor.