Unveiling Mechanistic Differences in the Curing of Copper and Silver Pastes for Heterojunction Solar Cells

Mhirsi O, Wengenmeyr MN, Huseynova Z, Hassan Zu, Bartsch J, Rapp BE (2026)

Publication Type: Journal article

Publication year: 2026

Journal

IEEE Journal of Photovoltaics Institute of Electrical and Electronics Engineers (IEEE)

DOI: 10.1109/JPHOTOV.2026.3714125

Abstract

Reducing silver consumption in silicon heterojunction (SHJ) solar-cell metallization motivates the use of conductive pastes based on mixed silver–copper (AgCu) fillers, but the curing mechanisms and resulting microstructures of such systems remain insufficiently understood. This work investigates an epoxy-based paste platform with AgCu or Ag fillers, formulated either with a linear amine hardener (HD1) or an anhydride curing system (HD2/CAT), to elucidate how curing chemistry and filler composition govern rheology, cure behavior, and conductivity. SEM/EDX is employed to assess AgCu particle morphology and copper exposure, rotational rheometry to track curing kinetics, and four-point probe measurements to evaluate the electrical conductivity of printed SHJ front-side fingers. The results show that incomplete silver shells on AgCu particles expose copper to Cu–amine complexation, inducing strong agglomeration and nonprintable rheology in epoxy–amine systems, whereas the anhydride-based formulation suppresses this interaction and yields stable, printable AgCu pastes, albeit with slower curing than a commercial AgCu reference paste. Using the selected epoxy resin (ER-2) in combination with the anhydride curing system provides suitable shear-thinning behavior, specific line resistance within the commercial range (6.4 μΩ cm), and reasonable adhesion on SHJ device stacks. These findings establish mechanistic links between curing chemistry, metal–polymer interactions, and functional properties, and thereby support the targeted design of low-temperature AgCu metallization pastes that balance material cost, conductivity, and reliability.

Involved external institutions

Fraunhofer-Institut für Solare Energiesysteme (ISE) / Fraunhofer Institute for Solar Energy Systems DE Germany (DE) Albert-Ludwigs-Universität Freiburg DE Germany (DE)

How to cite

APA:

Mhirsi, O., Wengenmeyr, M.N., Huseynova, Z., Hassan, Z.u., Bartsch, J., & Rapp, B.E. (2026). Unveiling Mechanistic Differences in the Curing of Copper and Silver Pastes for Heterojunction Solar Cells. IEEE Journal of Photovoltaics. https://doi.org/10.1109/JPHOTOV.2026.3714125

MLA:

Mhirsi, Oumaima, et al. "Unveiling Mechanistic Differences in the Curing of Copper and Silver Pastes for Heterojunction Solar Cells." IEEE Journal of Photovoltaics (2026).

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