Bringing cheaper, ‘greener’ lighting to market with inkjet-printed hybrid quantum dot LEDs

To make OLEDs cheaply and easily, researchers from the University of Louisville in Kentucky are developing new materials and production methods using modified quantum dots and inkjet printing. The team will discuss its work developing more commercially feasible QD-LED devices at the Conference on Lasers and Electro-Optics (CLEO: 2013) from 9-14 June in San Jose, California.

According to Delaina Amos, professor at the University of Louisville and principal investigator of the team’s efforts, the expense of materials and manufacturing processes has been a major barrier to using OLEDs in everyday lighting devices.

To inexpensively apply the quantum dots to their hybrid devices, the Louisville researchers use inkjet printing, popular in recent years as a way to spray quantum dots and OLED materials onto a surface with great precision. But unlike other groups experimenting with this method, Amos’ team has focused on adapting the inkjet printing technique for use in a commercial setting, in which mass production minimises expense and translates to affordable off-the-shelf products.

“We are currently working at small-scale, typically 1 x 1″ for the OLEDs,” Amos said. “The process can be scaled up from here, probably to 6 x 6″ and larger.”

Amos said there’s “a reason you don’t see OLED lights on sale at the hardware store”, though she added that they do find uses in small devices such as cameras, photo frames and mobile phone displays. To bring their QD-LEDs closer to becoming market-ready as household lighting appliances, Amos and her team have been synthesising new, less expensive and more environmentally friendly quantum dots. The team has also modified the interfaces between the quantum dots and other layers of the OLED to improve the efficiency with which electrons are transferred, allowing them to produce more efficient light in the visible spectrum.

In addition to their higher efficiency, wider range of colours and ability to be applied to flexible surfaces, Amos’ QD-LEDs also use low-toxicity materials, making them potentially better for the environment.

“Ultimately we want to have low cost, low toxicity and the ability to make flexible devices,” Amos said. The team has recently demonstrated small working devices and Amos hopes to have larger devices within the next several months.