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Protecting Quantum Dots with Siloxane Barriers
[ Issue 152 Page 4 ] Wednesday, March 29, 2017, 22:25:35 Tae Soo Kim Staff Reporter kimts96@kaist.ac.kr

In a joint effort, the research teams of Professor Byeong-Soo Bae of the Department of Materials Science and Engineering and Professor Doh Chang Lee of the Department of Chemical and Biomolecular Engineering were able to develop a quantum dot film enclosed by the compound siloxane. Remarkably, even at high temperatures and humidity, the film demonstrates stable emission intensity.

Quantum dots (QDs) are miniscule nanocrystals of semiconducting materials with variable emission wavelengths that can be determined by changing the size of the crystals. To take advantage of this property, QDs are coated on films or spread on LED light sources, and QDs are regarded as the light-emitting diodes (LEDs) of future displays.

Yet, problems arose when using QDs in actual applications. In an environment of high temperature and humidity, QDs easily oxidize, which significantly deteriorates the luminescence quality. To prevent oxidation, the QDs have to be encapsulated in an additional layer, away from moisture and oxygen. In the current displays, the encapsulation has been performed by inserting a highly expensive, protective film between the LEDs and QDs, which has prevented the displays from competing in the market.

Professor Bae and Professor Lee’s joint research team utilized the sol-gel condensation reaction of silane precursors. The chemical reaction manufactures glass or ceramics at low temperatures. By bringing this technology into play, the team was able to apply QDs in a heat-resistant siloxane polymer in a way such that the QDs lay inside siloxane cups that blocked heat and moisture.

Thanks to this process, the team was able to synthesize a film embedded with QDs that was able to retain high luminescence quality in an environment with temperatures reaching 85°C and humidity reaching 85%. The film was also tested in highly acidic and basic environments where it also performed remarkably.

Through the developments brought forward by the research team, the overall price of next-generation displays can be decreased profusely and Professor Bae expects that this technology “will make significant contributions to the display industry in the country”.

▲ Photoluminescence quantum yield vs. time of the team’s siloxane film and the normal acrylate film
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