Unlocking the potential of boronsilicate glass passivation for industrial tunnel oxide passivated contact solar cells. (30th November 2021)

• Record Type: Journal Article
• Authors: Liao, Baochen; Ge, Jia; Wu, Xinyuan; Wang, Qiang; Yeo, Reuben J.; Du, Zheren
• Is Part Of: Progress in photovoltaics. Volume 30:Number 3(2022)
• Page Start: 310
• Page End: 317
• Publication Date: 2021-11-30
• Subjects: BSG passivation -- BSG‐TOPCon -- front‐rear interlock -- industrial firing activation -- lower temperature paste; Solar cells -- Periodicals; Photovoltaic cells -- Periodicals; Solar power plants -- Periodicals; 621.31245
• DOI: 10.1002/pip.3519
• Languages: English
• ISSNs: 1062-7995

Abstract

Abstract: 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 Al2 O3 ‐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. Abstract : A simple and industrially viable method is presented to resolve the bottleneck faced by boronsilicate glass‐passivated TOPCon (BSG‐TOPCon) solar cells. With the two‐step method developed, the BSG layer demonstrated passivation performance comparable to other state‐of‐the‐art dielectric layers and improved the cell V oc by almost 10 mV. This work opens many new routes for the further improvement of BSG‐TOPCon solar cell efficiencies and gives us one good candidate for boron emitter passivation in device applications.