According to both companies, their collaboration looks to combine the benefits of the inkjet process with high-patterning resolution to drive a new generation of efficient and cost effective MicroLED displays, while also increasing colour purity and brightness, and improving overall pixel production tact time.
"We continue to find new applications of EHD that will meet the demands of the industry by offering an additive, completely waste-free process with higher resolution capabilities than lithography patterning," said Dr. Patrick Galliker, co-founder and CEO of Scrona. "While conventional inkjet printheads require inks of low viscosity, Scona has already demonstrated printing inks 1,000 times what they can process, paving the way for a much more efficient generation of MicroLED displays."
"Conventional inkjet printing is not a viable option for emerging MicroLED displays because they use much smaller pixels than QD-OLED displays," explained Dr. Norman Lüchinger, co-founder and CTO at Avantama. "By partnering with Scrona, we have been able to demonstrate that an OD greater than 1 can be obtained with a perovskite QD layer thickness below 2µm. This can reduce the printhead nozzle count by a factor of five and deliver a thin QD layer that improves the overall efficiency and production tact time of MicroLED display technology."
Scrona print head technology processes QD inks using EHD inkjet printing, whereby droplets are ejected from a nozzle by electrostatic forces. By exposing the ink to an electric field that originates from the outside of the nozzle, ions are pulled to the liquid surface and then start to create mechanical stress on the liquid body.
The density of ions at the surface are controlled by adjusting the intensity of the voltage that is used to create the electric field. The forces created inside the liquid are not uniform on the liquid surface, as is the case in traditional inkjet heads, but focus to the very centre of the nozzle while the liquid is continuously pulled out. Droplet size can be controlled by the applied voltages, including droplets that are one order of magnitude smaller than the nozzle itself.
Avantama perovskite QDs having the highest absorption coefficients among QDs, allowing printing thinner pixels with good optical density that significantly reduces tact time. Perovskite QDs have the highest weight-based absorption compared to others QDs, and this directly translates to very high OD/thickness values. One of the main reasons for this outstanding property is the inherently defect-tolerant nature of perovskites, that means a passivating shell is not required to enable high emission quantum yields.
