Improved LEDs glow after electricity switches off

When the power goes out, the lights go off. But with advances to afterglow organic LEDs, the lights might just stay on.

Xie et al. improved an organic light-emitting diode (OLED) that continues to glow once the voltage has been cut off. With an elongated afterglow time of 356 milliseconds, low driving voltages, and high efficiency, the OLED is an improvement over previous models. Such OLEDs could one day be used for applications such as emergency lighting and energy saving or low flicker lamps.

“Under electron-excitation, the afterglow OLEDs work in the same way as normal OLEDs, emitting steady-state electroluminescence, but after turning off the applied voltage, the devices exhibit afterglow emission,” said author Tao Ye.

The improved OLEDs were created through host-guest doping of a common electron transporting material – the host – and a widely used organic ultralong room temperature phosphorescence material – the guest. This method created an OLED with a high 1.47% external quantum efficiency and a lower driving voltage than previous afterglow OLEDs. The fabrication process is also simple and cheap. These advances open the door to the next generation of afterglow OLEDs and their use for practical applications.

“Such afterglow OLEDs could be used in energy saving lamps,” Ye said. “These lamps work in the same way as normal lamps in a power-on state but would still work after switching off the power, helping reduce electricity consumption.”

While the efficiency performance and afterglow lifetime of the OLED is not yet suitable for commercial applications, the researchers are working on improvements through new host-guest doping strategies and host material testing.

Source: “Achieving low driving voltage and high-efficiency afterglow organic light-emitting diodes through host-guest foping,” by Gaozhan Xie, Jiangchao Wang, Xudong Xue, Hui Li, Ningning Guo, Huanhuan Li, Danbei Wang, Mingguang Li, Wei Huang, Runfeng Chen, and Ye Tao, Applied Physics Reviews (2022). The article can be accessed at https://doi.org/10.1063/5.0093704 .

This paper is part of the Flexible and Smart Electronics Collection, learn more here .