Influence of local surface defects on the minority-carrier lifetime of passivating-contact solar cells

Unlocking the full potential of passivating contacts, increasingly popular in the silicon solar cell industry, requires determining the minority carrier lifetime. Minor passivation drops limit the functioning of solar cells; however, they are not detected in devices with open-circuit voltages below 700mV. In this work, simulations and experiments were used to show the effect of localized surface defects on the overall device performance. Although the defects did not significantly affect lifetime measurements prior to electrode deposition or open-circuit voltage measurements at standard-test conditions, they had a significant impact on the point of operation and, in turn, device efficiency (up to several percent efficiency drop). Furthermore, this study demonstrates that localized defects can have a detrimental effect on well-passivated areas located several centimeters away through electrical connection by the electrode. This leads to a low-injection lifetime drop after electrode deposition. Thus, commonly measured lifetime curves before metallization (and therefore internal voltage) are usually not representative of their respective values after metallization. The low-injection lifetime drop often observed after electrode deposition can be derived from such local surface defects and not from a homogeneous passivation drop.