Korean researchers developed a key technology that enables the customized production of polymer light emitting diodes, which is necessary for future display technology.
SNU College of Engineering (Dean Kookheon Char) announced on the 2^nd that SNU Professor Yongtaek Hong’s research team(Researcher Jong Jang Park) developed solution-processed polymer light emitting diodes that allows the customized formation of transparent and conductive polymer top anodes and Ag bottom cathodes by using inkjet printing.
Recently, various researches have been conducted for the production of inexpensive future display of large areas, including windows, ubiquitous information display, and attachable and disposable displays. The limitation here was that, with the conventional vacuum coating method, masks had to be individually fabricated according to the required design.
The research team was inspired by inkjet printing, which allowed unconstrained patterning for the electrode fabrication. They formed an Ag bottom cathode upon a glass and plastic substrate. After creating several functional layers including the light emitting layer, they transferred the polymer top anode created with inkjet printing to complete the device.
In particular, the transfer printing method could minimize the damage to the underlying organic layers that may occur during the solution process to create the top anode. To obtain smooth transfer characteristics, the team formulated an adhesive and conductive polymer ink. They applied several methods of adjusting the adhesion between the substrate and the film during the multistep transfer printing process.
With this method, the team created various forms of light-emitting logos and light emitting arrays of narrow line width. Furthermore, they were the first to produce all solution-processed passive PLED arrays. As a result, they were able to demonstrate that customized display devices could be manufactured with a dramatically simpler method compared to conventional display technologies.
Professor Yongtaek Hong explained, “We succeeded in developing all solution-based polymer light emitting diodes and creating high efficiency customizable light emitting diodes at the same time. It will be possible to expand application fields and implement various future displays by developing large area low cost processing technology.”
The results were published online on June 20^th in the internationally renowned journal ‘Advanced Functional Materials’. The research was conducted as a result of ‘Research program for the key technologies of materials and devices for future display’, which was supported by the Ministry of Trade, Industry and Energy and Korea Display Industry Association. The program was funded by Samsung Display.

Professor Yongtaek Hong, Researcher Jong Jang Park / Photo provided by SNU

Source: http://ee.snu.ac.kr/community/news?bm=v&bbsidx=49024 

Translated by: Jee Hyun Lee, English Editor of Department of Electrical and Computer Engineering, jlee621@snu.ac.kr