Unlocking the potential of boronsilicate glass passivation for industrial tunnel oxide passivated contact solar cells

In this work, we present a breakthrough in boronsilicate glass (BSG) passivated industrial tunnel oxide passivated contact (i-TOPCon) solar cells. We find that a high-temperature firing process significantly improves the front side BSG passivation quality; however, the use of such high-temperatures is undesirable for metallization as it could lead to more junction damage by the metal paste spikes. In this study, we present a simple and industrially viable method to resolve this dilemma. With a high-temperature industrial firing activation step to maximize the potential of BSG passivation, a low emitter saturation current (J(0e)) of 34 fA/cm(2) has been achieved, demonstrating excellent boron emitter passivation that is comparable to state-of-the-art SiO2 and Al2O3-based passivation methods on similar structures and boron emitters. Applying this solution to cell device, the open-circuit voltage (V-oc) is improved by about 6 mV, corresponding to an absolute cell efficiency improvement of about 0.2%. Furthermore, after activating the BSG passivation, a lower temperature paste could be used at the rear side which further improves the V-oc by around 3 mV. Combined together, an overall improvement of V-oc close to 10 mV is achieved, propelling the cell V-oc into the 690-mV era. The effectiveness of this solution was also verified in a mass production line, with average cell efficiencies of around 23.2% (0.5% more than the baseline) and a maximum cell efficiency and V-oc of 23.4% and 693 mV, respectively. This work opens new routes for further improving conventional solar cell efficiencies, in particular for BSG-passivated TOPCon solar cells.