Nanostructures Enable Step Toward OLED Lasers

Organic LEDs made with finely patterned nanostructures can produce bright, low-power light sources, a key step toward making organic lasers.

Researchers have long dreamed of building organic lasers, but they have been hindered by carbon-based semiconductors’ tendency to operate inefficiently at the high currents required for lasing due to overheating.

Charge diffusion in the transport region of an OLED. Courtesy of Thuc-Quyen Nguyen/UCSB.

“Lasers operate in extreme conditions with electric currents that are significantly higher than those used in common displays and lighting,” said professor Dr. Thuc-Quyen Nguyen of the University of California, Santa Barbara. “At these high currents, energy loss processes become stronger and make lasing difficult.”

Nguyen and her team collaborated with researchers in Japan to find a way around this problem and take a step toward realizing organic lasers.

They showed that the efficiency roll-off problem can be solved by using electron-beam lithography to produce finely-patterned OLED structures. The small device area supports charge density injection of 2.8 kA/cm² while maintaining 100 times higher luminescent efficiency than previously observed.

“An important effect of suppressing roll-off is an increase in the efficiency of devices at high brightness,” said professor Dr. Chihaya Adachi of Kyushu University. “This results in lower power to obtain the same brightness.”

The research was published in Applied Physics Letters (doi: 10.1063/1.4913461).

For more information, visit www.kyushu-u.ac.jp and www.ucsb.edu.