Influence of Particle Shape and Size in Copper‐Based Low‐Temperature Metallization Paste for Solar Cells

This study systematically explores the impact of particle shape, size, and distribution—comparing monomodal to bimodal architectures—on the rheological, microstructural, and electrical properties of copper‐based low‐temperature screen‐printing pastes. Monomodal formulations reveal the advantages of flake‐shaped Ag‐coated Cu (AgCu)‐particles in promoting electrode conductivity via enhanced percolation, but face challenges in flow stability and print consistency. Shifting to bimodal systems by blending AgCu with submicron silver spheres leads to substantial improvements in packing density, finger definition, and resistivity of an optimized bimodal formulation yielded a minimum of 6.51 μΩ·cm after curing at 240 °C, closely matching commercial AgCu pastes while utilizing on average 6 wt% less silver in the metal loading. Scanning electron microscopy, 3D optical microscopy, and thermogravimetric analysis (TGA) show that electrical conductivity is influenced not only by particle geometry and metal loading, but also by particle‐batch characteristics and the thermal evolution of surface‐associated material. The TGA results reveal distinct thermal mass‐change behavior among the Ag powders and between AgCu‐S batches, highlighting the importance of interfacial properties, Ag‐shell integrity, and batch‐to‐batch reproducibility for electrical performance under the investigated curing conditions.