Researchers at KAIST have achieved high efficiency with OLED without using macroscopic lens. They used an external scattering medium to achieve an external quantum efficiency (EQE) of more than 50 percent in OLED stimulation. The research, led by Professor Seunghyup Yoo and PhD candidate Jinouk Song, was published in Nature Communications on August 10th, 2018.

(Image:KAIST)

The team focused on the external scattering-based approach as it can maintain planar geometry and compatibility with flexibility. In addition, it can be produced in a large scale at low cost and causes no interference with electrical properties of OLEDs.

KAIST’s researchers developed an analytical methodology to theoretically predict structures that maximize efficiency. They combined the mathematical description of the scattering phenomena with the optical model for light emission within an OLED to rapidly predict the characteristics of many devices with various structures. With the approach, the KAIST team theoretically predicted the optimal combination of scattering layers and OLED architectures that can lead to maximum efficiency.

(Image: KAIST; Photographs of OLEDs with SiO₂ -embedded scattering layers according to scatterance)

Following the prediction, the team managed to reach an EQE of 56 percent and a power efficiency of 221 lm/W with OLED by producing the optimal light scattering film and incorporated it to OLEDs. According to KAIST, this result is one of the highest efficiencies ever realized for an OLED unit device without the help of a macroscopic lens or internal light extraction structures.

Reference:
Song, J., et al. Lensfree OLEDs with over 50% external quantum efficiency via external scattering and horizontally oriented emitters, Nature Communications, volume 9, Article number: 3207 (2018). DOI: 10.1038/s41467-018-05671-x