PULSED LASER MELTING FOR TOPCON TECHNOLOGY: NEW ROUTES TO HIGHER EFFICIENCY

Tunnel oxide passivating contacts (TOPCon) are a leading route to high-efficiency crystalline-silicon (c-Si) solar cells. The core structure poly-Si/SiOx/c-Si uses an ultrathin (<2 nm) tunnel oxide to passivate the c-Si surface while a heavily doped poly-Si layer provides carrier selectivity. Carrier transport is dominated by tunneling through the SiOₓ layer, although direct conduction through local oxide openings (“pinholes”) in textured contacts can also contribute. In this work we investigate both pathways and show how pulsed laser melting (PLM) can be used to enhance performance without sacrificing passivation. Using nanosecond-PLM, we achieve hyperdoping of poly-Si with boron and gallium beyond their equilibrium solid-solubility limits, yielding low-resistivity contacts while preserving the SiOₓ/c-Si interface. The surface-localized heating inherent to PLM suppresses boron diffusion through SiOₓ that typically degrades passivation in conventional processes [1,2]. Thermal-stability assessments further support the robustness of the laser-treated stacks and their suitability for industrial integration. For the pinhole-mediated pathway, we explore PLM as a method to create nanoscale openings at the tips of pyramidal-textured cells while maintaining passivated contacts on the pyramid facets [3]. Atomic force microscopy (AFM) tracks morphology as a function of laser parameters, and conductive AFM (c-AFM) provides spatially resolved current maps that clarify carrier transport through individual pinholes [3,4]. Overall, PLM enables hyperdoped, low-resistance poly-Si contacts with preserved passivation and controlled pinhole formation compatible with textured surfaces, together outlining a viable route to TOPCon performance gains with manufacturable process windows. ref. [1] Chen, K. et al., Electrical Analysis of Pulsed Laser Annealed Poly -Si: Ga/SiOx Passivating Contacts. (2023), AIP Conference Proceedings, 2826 (020002) [2] Chen, K., et al., Pulsed Laser Annealed Ga Hyperdoped Poly‐Si SiOx Passivating Contacts for High-Efficiency Monocrystalline Si Solar Cells (2023), Energy & Environmental Materials, e12542. [3] Pauls, S. et al. (2025) Patent: Silicon Wafer Having Passivating Contacts (US20250098359). [4] Submitted paper: Laser Enabled Nanopinholes for Silicon Solar Cells with Polycrystalline Si/SiOx Passivating Contacts.