Laser enhanced contact optimization on rear-junction double-side TOPCon solar cells: Detailed analysis of Metal-Si contact properties and interfacial microstructures

Double-side tunnel oxide passivated contact (DS-TOPCon) solar cells offer a promising pathway to surpass the efficiency limits of conventional n -TOPCon solar cells; however, their performance is often constrained by the high contact resistivity ( ρ c ) and metal-induced recombination current ( J 0,met ) at the hole-selective p -TOPCon layer. In this work, we investigate the combined impact of firing temperature and laser-enhanced contact optimization (LECO) on the electrical and interfacial properties of both n -TOPCon and p -TOPCon layers. LECO effectively decouples ρ c from firing temperature, achieving low ρ c values of ≈0.4 mΩ-cm 2 for n -TOPCon on textured surface and ≈2.6 mΩ-cm 2 for p -TOPCon on planar surface at firing temperatures 30–50 °C below typical industrial firing conditions. Despite these benefits, LECO induces a small but measurable degradation in open-circuit voltage (≈5 mV) in DS-TOPCon solar cells, attributed to increased surface and junction recombination. Microstructural analysis reveals LECO-induced enlargement of embedded Ag crystallites and the formation of current-fired contact (CFC), providing direct physical insight into the changes in ρ c and recombination behavior. By co-optimizing the firing temperature and LECO treatment, we demonstrate 23.2%-efficient rear-junction DS-TOPCon solar cells fabricated using a cost-effective codiffusion process. Device simulation further projects that, with readily available advanced technologies, rear-junction DS-TOPCon solar cells can exceed 26% efficiency.