By BizLED Bureau
Mar 9, 2016: To enable mass production of Organic Light Emitting Diodes (OLED), highly efficient, solution-processed fluorescence OLEDs have been created using “pure-organic” emitters.
Regular or conventional OLEDs use phosphorescent emitters which exhibit a high internal quantum efficiency of close to 100 percent. As these emitters are made of expensive heavy metals like iridium and platinum into phosphorescent metal complexes, they cannot be processed commercially due to high manufacturing costs.
Researchers at Pohang University of Science & Technology (Postech) have implemented pure-organic thermally activated delayed fluorescence (TADF) emitters which show a very high IQE of nearly 100 percent without incorporating precious metals. This has helped to overcome the disadvantage of using precious metals. TADF emitters greatly reduce the cost of synthesis offering the advantages of versatile molecular design and easy synthesis using pure-organic molecules.
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The research team created a multifunctional buffer hole injection layer (HIL) that increased the injecting capability to the emitting layer (EML) because of high work function. The inexpensive, simple solution-process to fabricate the TADF-OLEDs was introduced by solving fundamental problems which limited the high efficiency in solution-processed TADF-OLEDs.
The researcher team further improved the luminescence efficiency of TADF-OLEDs by preventing exciton reaching the HIL/EML interface. They came to a conclusion that a new polar aprotic solvent improved the device efficiency by improving the solubility of pure-organic TADF emitters. This reduced the surface unevenness and the aggregation of dopants, and managing the exciton quenching in the emitting layer.
This breakthrough in technology is a big leap toward the development of less expensive and solution-processed OLED displays and solid-state lightings. This method uses cost-effective, pure-organic molecules and simple solution process to realize the extremely high-efficiency solution-processed OLEDs. The improvement in solution processed TADF-OLEDs could resolve the shortcomings of a complex and expensive vacuum-deposition process, lowering the production cost of the devices.