Cheaper OLED Displays Without Precious Metals

Researchers have come up with a more cost-effective method of producing highly efficient organic light-emitting diode (OLED) displays, commonly used in HD TVs.

AsianScientist (Mar. 15, 2016) – A team based in South Korea has developed cheaper, highly efficient, solution-processed fluorescence organic light-emitting diodes (OLEDs) using pure-organic thermally-activated delayed-fluorescence (TADF) emitters. The research was published in Advanced Materials.

Conventional OLEDs use phosphorescent emitters which have shown high internal quantum efficiency (IQE) of nearly 100 percent. However, they contain precious heavy metals such as iridium and platinum; these limit their commercialization.

In order to overcome these challenges, the research team used pure-organic TADF emitters, which show a very high IQE of nearly 100 percent but do not require precious metals. Furthermore, TADF emitters have the advantage of easy synthesis using pure-organic molecules and versatile molecular design, thus reducing costs.

The team, led by Professor Lee Tae-Woo from the department of materials science and engineering at Pohang University of Science and Technology, also introduced an inexpensive, simple solution-process to fabricate the TADF-OLEDs by solving fundamental problems which limit the high efficiency in solution-processed TADF-OLEDs.

They used a multi-functional buffer hole injection layer that can increase the hole injection capability to the emitting layer due to its high work function. They also improved the luminescence efficiency of TADF-OLEDs by preventing exciton quenching at the interface between the hole injection layer and emitting layer.

Furthermore, they used a new polar solvent that improved the device efficiency by increasing the solubility of pure-organic TADF emitters, reducing the surface roughness and the aggregation of dopants, and managing the exciton quenching in the emitting layer.

This improvement in solution processed TADF-OLEDs addressses the challenges of a complex and expensive vacuum-deposition process and thus lowers the production cost of the devices. It is of prime importance to reduce the production cost of the devices for industrial mass production.

“This technology is a big leap toward the development of inexpensive and solution-processed OLED displays and solid-state lighting because this method uses only low-cost pure-organic molecules and simple solution-process to realize the extremely high efficiency solution-processed OLEDs,” said Lee.



The article can be found at: Kim et al. (2015) Highly Efficient, Simplified, Solution-Processed Thermally Activated Delayed-Fluorescence Organic Light-Emitting Diodes.

———

Source: Pohang University of Science and Technology; Photo: Shutterstock.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

Asian Scientist Magazine is an award-winning science and technology magazine that highlights R&D news stories from Asia to a global audience. The magazine is published by Singapore-headquartered Wildtype Media Group.

Related Stories from Asian Scientist