Inkjet Print Process Devised for Quantum Dot Organic LEDs

The vials on the left contain quantum dots made with cadmium selenide in a solution; the vial on the right contains the solvent without quantum dots. (Delaina Amos).

Engineers at University of Louisville in Kentucky developed a process for making organic light-emitting diodes (OLEDs) with quantum dots and applied with inkjet printing, a common manufacturing technology. The findings of the research team led by Louisville engineering professor Delaina Amos will be presented next week at the Optical Society’s Conference on Lasers and Electro-Optics in San Jose, California.

OLEDs are solid-state devices made with thin films of organic molecules that generate light when an electric current passes through. Displays made with OLEDs can be made much thinner and flexible, and use less power than LED or liquid-crystal displays found in conventional flat-screen televisions or computer monitors. However, widespread manufacturing of OLEDs has been held back because of the cost of materials and their expensive production processes.

The Louisville team aims to create an OLED manufacturing technique with inkjet printing, an established manufacturing process widely used in commercial settings. Their methods use quantum dots made of cadmium selenide, an inorganic material, forming a hybrid type of OLED. Quantum dots are nanoscale semiconductor crystals, which have among other properties photoelectric effects.

These synthesized quantum-dot OLEDs, says Amos, are more efficient than earlier OLEDs and can present a wider spectrum of colors. She adds that they are also less expensive to produce and more environmentally friendly, using low-toxicity materials.

Amos and colleagues demonstrated their technology using cadmium selenide quantum dots in a solution applied with an inkjet printer. The OLEDs are applied in layers, with interfaces between the layers designed to improve the efficiency with which electrons are transferred through the device.

The demonstrations so far created small-scale (1-inch by 1-inch square) OLED devices, but Amos says they can be scaled up to 6 by 6 inches or larger within the next few months. “Ultimately,” notes Amos, “we want to have low cost, low toxicity, and the ability to make flexible devices.”

Read more:

• Merck, Seiko Epson to Partner on Organic LED Inkjet Inks
• Project to Study Light-Enabled Quantum Dot Circuits
• New Quantum Dot Material Boosts Solar Cell Efficiency
• Nanotech Solar Energy Paint Developed
• Manufacturing Process Devised for More Economical LEDs

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