Reviewed by Lexie CornerFeb 25 2025
Researchers from the University of Turku developed a theoretical model using novel quantum states known as polaritons to predict a significant increase in the brightness of organic light-emitting diodes (OLEDs). The successful integration of polaritons into OLEDs requires the development of new materials, presenting a challenge for real-world applications. The study was published in Advanced Optical Materials.
The picture shows a standard blue OLED with a width of 15 mm and an emitting pixel width of 2 mm. A polariton OLED would be obtained by replacing the thin films below and above with a semi-transparent material with a thickness of 10-100 nm. It would be impossible to separate them from the image. Image Credit: Mikael Nyberg and Manish Kumar
OLED technology is now widely used as a light source in high-end display devices, including smartwatches, laptops, TVs, and smartphones.
Despite their versatility and environmental benefits, OLEDs have only a 25 % chance of efficiently and quickly emitting photons, which can make them slow at converting electric current into light. This is a critical factor in limiting their brightness, as OLEDs are typically dimmer than other light technologies.
To address this challenge, researchers from Cornell University and the University of Turku have proposed a predictive model.
OLEDs are electronic components made from organic carbon-based materials that emit light when exposed to an electric current. Unlike liquid crystal displays (LCDs), which rely on LED backlighting, OLED displays generate light directly from the pixels.
When organic emitters are placed between two semi-transparent mirrors, they can couple with confined light, forming new light-matter hybrid states known as polaritons.
By fine-tuning these states, researchers aim to find the optimal condition where the remaining 75 % of dark states transform into bright polaritons, improving the efficiency and brightness of OLEDs.
While the general idea of using polaritons in OLED technology is not entirely original, a theory that examines the boundaries of performance gains has been missing. In this work, we carefully examined where the polariton sweet spot lies in different scenarios. We found that the strength of the polaritonic effect in OLEDs’ performance depends on the number of coupled molecules. The fewer, the better.
Konstantinos Daskalakis, Associate Professor, University of Turku
“With the molecules we studied and a single coupled molecule, the efficiency improved significantly. The dark-to-bright conversion rate increased by a whopping factor of 10 million at best,” said Olli Siltanen, Postdoctoral Researcher.
The polaritonic effect was minimal when many molecules were present, meaning that simply adding mirrors to modern OLEDs will not improve their dark-to-bright conversion rate.
“The next challenge is to develop feasible architectures facilitating single-molecule strong coupling or invent new molecules tailored for polariton OLEDs. Both approaches are challenging, but as a result, the efficiency and brightness of OLED displays could be significantly improved,” explained Daskalakis.
Efficiency and brightness limitations have restricted the widespread use of OLEDs, especially compared to conventional inorganic LEDs. The findings from this study offer a potential pathway for improving OLED efficiency and performance.
Journal Reference:
Siltanen, O., et al. (2025) Enhancing the Efficiency of Polariton OLEDs in and Beyond the Single-Excitation Subspace. Advanced Optical Materials. doi.org/10.1002/adom.202403046