Purer colour emission through strong light-matter coupling
Exciton Science researchers have unveiled a novel approach that could enhance the performance of organic light-emitting diodes (OLEDs), the technology behind vibrant displays in smartphones and TVs.
OLEDs work by using organic molecules to emit light when an electric current is applied. However, a significant challenge has been the formation of 'triplets', which are weakly emissive and can reduce the efficiency and brightness of the OLEDs.
To address this, researchers have been exploring thermally activated delayed fluorescence (TADF) emitter molecules, which can convert these 'triplets' back into bright 'singlets', thereby improving the light emission and potentially enabling 100% efficiency.
However, traditional TADF molecules have their own set of challenges, including limited colour purity. Enter multi-resonance TADF (MR-TADF) emitters, a newer generation of molecules that promise better color purity and efficiency. Still, these have been plagued by issues like molecular aggregation at high molecular loading due to their planar molecular geometry, which can lead to inefficiencies.
To address this, an Exciton Science team based at the University of Sydney and the University of Melbourne explored the realm of strong light-matter interactions. By placing the MR-TADF molecules inside an optical cavity, they created a unique environment where light and matter interacted intensely, forming hybrid particles called 'polaritons'. These polaritons can efficiently transfer energy to the bright polariton states, leading to enhanced light emission.
The team, led by Dr Inseong Cho and Associate Professor Girish Lakhwani, synthesized a new MR-TADF molecule, OQAO(mes)2, which demonstrated impressive properties when placed inside an optical cavity. Notably, emission through molecularly aggregated states, known as ‘excimers’, was effectively suppressed even at high dye loading, by which colour purity is enhanced. Furthermore, they observed a 33% enhancement in the rate of converting 'triplets' to 'singlets', which could contribute to brighter emission.
The results have been published in the Journal of Materials Chemistry C.
The study's findings underscore the potential of optical cavities in enhancing OLED performance, opening doors for further advancements in display technology and organic semiconductor lasing applications.
As the demand for high-quality displays continues to grow, innovations like these are set to play a pivotal role in shaping the future of visual technology.
