Importance of the Heat Treatment Scheme on Self-Reducing Reactive Silver Inks

Journal Article · Mon Oct 23 00:00:00 EDT 2023 · ACS Applied Electronic Materials

DOI:https://doi.org/10.1021/acsaelm.3c01082· OSTI ID:2397023

DiGregorio, Steven J. ^[1]; Raikar, Subbarao ^[2]; Hildreth, Owen J. ^[2]

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1. Colorado School of Mines, Golden, CO (United States); Colorado School of Mines
2. Colorado School of Mines, Golden, CO (United States)

Self-reducing reactive silver inks can print high-quality silver at reasonable temperatures. While numerous studies have explored the impact of processing temperature on electrical properties, the role of the heat treatment scheme has not yet been studied. Common heat treatment schemes include printing and drying inks at room temperature before heat treatment, performing heat treatments while the inks are still wet, and directly printing the inks onto heated substrates. Each scheme generates distinct heat transfer and mass transport kinetics that can affect the silver morphology and electrical properties. However, to date, the impact of different schemes has not been systematically investigated. To address this knowledge gap, this work investigates how different heat treatment schemes impact metal formation, sintering, and the resultant electrical properties of printed self-reducing reactive silver inks. Heat treatment on room-temperature dried inks and wet inks, with top-down (oven) and bottom-up (hot plate) heating sources, were compared. Inks dried at room temperature resulted in extremely porous films that required high heat treatment temperatures (>100 °C) for silver densification. However, these dried films could only densify locally, and their high initial porosities resulted in voids and high resistances (~0.6 Ω mm^–1) even after heat treatments above 300 °C. Inks that were wet during heat treatment showed moderate improvements in electrical properties with resistances on the order of 0.4 Ω mm^–1 at heat treatments of 250 °C. Printing reactive inks directly onto heated substrates yielded the best low-temperature results, with 0.46 Ω mm^–1 (5.5 × bulk silver) line resistances achieved at only 90 °C. Overall, this work’s experimental results provide detailed insights into why printing onto a heated substrate results in superior electrical performance compared to more common heat treatment schemes. Additionally, controlling where the precipitation reaction occurs is critical to controlling the film morphology and properties. As a result, this work shows that even an ammonia-based silver reactive ink can achieve good, low-temperature electrical properties with the proper heat treatment scheme.

• Research Organization: Colorado School of Mines, Golden, CO (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE)
• Grant/Contract Number: EE0008166
• OSTI ID: 2397023
• Journal Information: ACS Applied Electronic Materials, Journal Name: ACS Applied Electronic Materials Journal Issue: 1 Vol. 6; ISSN 2637-6113
• Publisher: ACS Publications
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
conductive ink
electrical properties
heat treatment
interfaces
low-temperature metallization
morphology
particle-free silver ink
printed electronics
reactive silver ink
redox reactions
silver