Local p + Poly‐Si Passivating Contacts Realized by Direct FlexTrail Printing of Boron Ink and Selective Alkaline Etching for High Efficiency TOPCon Based Solar Cells

• DOI: 10.1002/pip.3901
• Publication Date: 2025-02-20T02:31:06Z
• Authors: Berkay Uygun; Sven Kluska; Jana‐Isabelle Polzin; Jörg Schube; Mike Jahn; Katrin Krieg; Raşit Turan; Hisham Nasser
• Keywords: Passivation

ABSTRACT In this work, we demonstrate the formation of local boron‐doped, SiOₓ/p + poly‐Si structures using wet chemical etching by direct printing boron‐ink. FlexTrail uses a very hollow (orders μm for diameter) glass capillary tube filled with boron ink onto silicon substrate. This process represents mask‐free approach TOPCon structures, enabling high‐efficiency tunnel oxide passivating contact (TOPCon) solar cells. The factors influencing etch‐back selectivity between intrinsic and boron‐doped were thoroughly investigated. It was determined that pre‐treatment diluted HF (1 wt%) prior to removal in KOH solution is most critical step achieve optimal etch selectivity. treatment effectively removes native on while preserving silicate (BSG) layer p poly‐Si, facilitating selective structures. Line widths ranging from 24.0 100.5 planar surfaces 40.0–86.0 textured achieved. allows significantly lower (and higher) feature sizes, but its fine‐line potential not fully exploited here due alignment challenges during post‐processing. Test line grid exhibited maximum open‐circuit voltage (𝑖V OC 720 mV lowest saturation current density (𝐽 0𝑆𝐸 ) ~90–120 fA/cm 2 . developed will be integrated into cells, where strategically placed under metal contact, near future.