Industrial roll-to-roll inkjet printing of silver is feasible

Holst Centre has demonstrated the production of high-quality silver conductive structures using inkjet printing in high-speed roll-to-roll production. The team has produced 50-micron features with 5 times the resistivity of bulk silver on plastic substrates at rates up to 20 meters per minute. The technique has already been used to print antennas for RFID tags on paper, and could be applied to cut the cost of organic photovoltaic (OPV) solar panels, building-integrated photovoltaics and other printed electronic applications.

Roll-to-roll production of printed electronics could dramatically cut the cost of applications ranging from RFID tags and smart packaging to solar panels and environmentally friendly indoor lighting. Conductive structures are a fundamental building block of any electronics application. This latest development from Holst Centre brings roll-to-roll production a step closer, by proving the feasibility of creating these structures reliably using a high-volume roll-to-roll process.

In the Holst Centre process, the required structures are printed onto flexible plastic foils using standard industrial inkjet printer heads, then dried with near infrared light and cured using Holst Centre's proprietary photonic sintering technique. Operating at up to 20 meters per minute, the process produces fine structures with high conductivity, low defectivity and minimal foil deformation. Moreover, the drying and curing equipment fits within a 60 cm footprint, allowing easy integration into production lines.

"Inkjet printing offers manufacturers a lot of flexibility in what they can print, so it is ideal for prototyping testing and pilot production. But it is extremely difficult to print reliably on plastic substrates in a roll-to-roll set up as the inks are around 95% solvent. By combining near infrared drying and photonic sintering with our knowledge of handling printed structures, we've created a high-speed, low-temperature process that delivers better conductivity than thermal sintering and is suited to for plastic substrates," says Eric Rubingh, a researcher within Holst Centre's Printed conductive structures on flexible substrates program.

Working with several partners in the EU-funded LOTUS project, Holst Centre researchers have already applied the new high-speed process to create antennas for RFID tags on paper at 20 meters per minute. In this latest achievement, the process has been applied on plastic substrates, which are considerably more challenging to work with.

As a contactless technique, inkjet printing is ideal for printing structures onto sensitive substrates. Therefore it is expected that Holst Centre's new process will be first used industrially to produce the top electrode for OPVs, potentially cutting production costs for these environmentally friendly and esthetically pleasing renewable energy sources.

You can see the process in action on our YouTube channel.

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