By BizLED Bureau
July 12, 2017: Flexible organic LED (OLED) displays are picking up in popularity due to their applications in smartphones and color televisions, which were widely showcased at the Consumer Electronics fair in January in Las Vegas. However, OLED displays are still not affordable as their production cost is high and hence are not produced en mass.
With the aim to make flexible OLED displays cost-effective to produce en masse, Massachusetts Institute of Technology (MIT) has been researching for years. MIT spinout Kateeva has now developed an inkjet printing system for OLED displays based on years of MIT research that they claim can cut down manufacturing costs to such an extent that it can produce flexible and large-screen models on a mass scale.
“Kateeva aims to fix the last ‘Achilles heel’ of the OLED-display industry, which is manufacturing,” said Kateeva co-founder and scientific advisor Vladimir Bulovic, the Fariborz Maseeh Professor of Emerging Technology, who co-invented the technology.
Kateeva has developed a technology platform called YIELDjet, which is a large version of an inkjet printer. It places large glass or plastic substrate on a long and wide platform. A component with custom nozzles moves fast across the substrate, coating it with OLED and other materials just like a printer drops ink on papers.
Tools to make OLED process easy
Kateeva has also developed two tools for two specific areas in the OLED production process. These tools use YIELDjet platform. The first tool YIELDjet FLEX can enable thin-film encapsulation (TFE). TFE is the process that gives thinness and flexibility to OLED devices; Kateeva hopes that YIELDjet FLEX will be available in the market by the end of the year.
The second tool, which will also be available by the end of the year, will cut defects associated with patterning OLED materials onto substrates, in order to make producing 55-inch screens easier, which will eventually cut down manufacturing cost.
“By boosting yields, as well as speeding up production, reducing materials, and reducing maintenance time, the system aims to cut manufacturing costs by about 50%,” said Kateeva co-founder and CEO Conor Madigan SM 02 PhD 06. “That combination of improving the speed, improving the yield, and improving the maintenance is what mass-production manufacturers want. Plus, the system is scalable, which is really important as the display industry shifts to larger substrate sizes,” he said.
The other Kateeva co-founders and technology co-inventors are MIT Provost Martin Schmidt, now a scientific advisor; Jianglong Chen SM 03, PhD 07, now program director; and Valerie Leblanc PhD 07, now staff scientist.
YIELDjet FLEX solves TFE issues
TFE method coats flexible OLED screens with a barrier that is solid but bendable. However, it is prone to contamination. The traditional TFE processing methods is slow and expensive and also wastes materials. It also cannot tackle the moisture issues, is deadly to OLEDs. Due to these defects, the contaminated OLED displays need to be discarded and hence to make up the loss, manufacturers increase the retail prices.
YIELDjet FLEX has been developed to solve these TFE issues. The printer in encased in a nitrogen chamber, cutting exposure to oxygen and moisture, as well as cutting contamination with particles. This is truly an innovation. ?Low-particle nitrogen is the best low-cost, inert environment you can use for OLED manufacturing,? Madigan said.
“In the TFE process, the YIELDjet coats organic films over the display area as part of the TFE structure. The organic layer flattens and smoothes the surface to provide ideal conditions for depositing the subsequent layers in the TFE structure. Depositing onto a smooth, clean surface dramatically improves the quality of the TFE structure, enabling high yields and reliability, even after repeated flexing and bending,” Madigan said.
Kateeva has also developed a system that is an improvement over the traditional vacuum thermal evaporation (VTE) technique. VTE places a substrate inside a vacuum chamber, and sprays through the shadow mask a vapor of OLED material in precise patterns of red, green, and blue. But materials get wasted when the vapor is sprayed on the mask and chamber. Coating the chamber and mask can also lead to particle contamination as the material flakes off, so excessive cleaning maintenance is required, Madigan said. Smaller shadow masks are more reliable, he said.
The system developed by Kateeva is enclosed in a nitrogen chamber, positions substrates large enough for six 55-inch displays beneath the print heads, which contain hundreds of nozzles. These nozzles are tuned to deposit tiny droplets of OLED material in exact locations to create the display’s pixels. “Doing this over three layers removes the need for shadow masks at larger scales,” Madigan said.
As with its YIELDjet FLEX system, Madigan says this YIELDjet product for OLED TV displays can help manufacturers save more than 50% over traditional methods.
In January, Kateeva partnered with Sumitomo, a leading OLED-materials supplier, to optimize the system for volume production.
Source: Massachusetts Institute of Technology