KAIST research team has fabricated a siloxane-encapsulated quantum dot film that exhibits stable emission intensity over one month even at high temperatures and humidity.

Quantum dots (QDs) are tiny particles or nanocrystals of semiconducting materials. Their emission wavelength can easily be adjusted by changing their sizes that are just a few nanometres. A wide spectrum of their colours can also achieve ultra-high definition displays in next-generation LEDs.

Due to these characteristics, QDs as a polymer resin in dispersed form are coated in a film as they are spread on an LED light source. They are thus considered to be crucial for next generation displays.

Despite their exceptional optical properties, however, QDs are easily oxidised in a high temperature and high humidity environment and, as a result, this greatly deteriorates their luminescence quality (quantum efficiency). Therefore, they are encapsulated in an extra thin layer to block oxygen and moisture.

The research team applied the sol-gel condensation reaction of silane precursors with QDs. This technology uses the reactions of chemical substances to synthesise ceramics or glass at a low temperature.

 
KAIST quantum dot film fig1 (cr) Figure 1: Siloxane-encapsulated quantum dot (QD) films showing performance stability in boiling water.  

The team applied QDs in a heat-resistant siloxane polymer by employing this technology. The siloxane resin acted as a cup holding the QDs, and also blocked heat and moisture. Thus, their performance can be maintained without an extra protective film.

QDs are evenly dispersed into the resin from a chemical process to fabricate a QD embedded film and retained the high quality luminescence not only at a high temperature of 85°C and in a high humidity of 85%, but also in a high acid and high base environment. Remarkably though, the luminescence is actually increased in the high humidity environment.

 
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