Periodic Reporting for period 4 - PLAS-OLED (Polariton Assisted White Light Generation in Organic Light-Emitting Diodes)
Reporting period: 2023-11-01 to 2025-09-30
Artificial light is essential to modern life, yet its growing demand significantly increases energy consumption and environmental impact. Organic light-emitting diodes (OLEDs) offer an attractive alternative to conventional semiconductor lighting technologies because they combine high efficiency with the potential for lightweight, flexible, and material-efficient fabrication. However, their wider deployment in lighting applications has been limited by intrinsic material challenges, including low electrical conductivity, sensitivity to environmental degradation, and efficiency losses at high operating power. As a result, current OLEDs remain largely confined to display technologies rather than large-scale lighting.
The PLAS-OLED project addressed this challenge by exploring whether the performance and stability limitations of OLEDs could be overcome by engineering their photonic environment. Specifically, the project investigated the integration of OLED emitters into optical microcavities that confine light and modify the interaction between emitted photons and molecular excitations. Under suitable conditions, this interaction leads to the formation of hybrid light–matter states known as polaritons.
The overall objective of PLAS-OLED was to determine whether polaritonic effects could be harnessed to improve the efficiency and spectral performance of OLEDs and white OLEDs (WOLEDs), while also enabling simplified device architectures based on single, more stable emitters. By controlling both the emission processes inside the device and the escape of photons from it, the project aimed to establish new strategies for achieving efficient light generation without relying on complex multi-emitter systems.
Over the course of the project, we demonstrated that polariton formation provides a viable pathway to selectively influence key emission processes in OLEDs. Importantly, our findings show that strong light–matter coupling does not universally enhance all radiative processes, but instead primarily affects inefficient recombination pathways and emission disperssion. This provides a realistic framework for using photonic design to suppress loss mechanisms and improve device operation. The project therefore concludes that polariton engineering represents a promising strategy for enhancing OLED performance while supporting the development of more stable and potentially lower-impact lighting technologies.
The PLAS-OLED project addressed this challenge by exploring whether the performance and stability limitations of OLEDs could be overcome by engineering their photonic environment. Specifically, the project investigated the integration of OLED emitters into optical microcavities that confine light and modify the interaction between emitted photons and molecular excitations. Under suitable conditions, this interaction leads to the formation of hybrid light–matter states known as polaritons.
The overall objective of PLAS-OLED was to determine whether polaritonic effects could be harnessed to improve the efficiency and spectral performance of OLEDs and white OLEDs (WOLEDs), while also enabling simplified device architectures based on single, more stable emitters. By controlling both the emission processes inside the device and the escape of photons from it, the project aimed to establish new strategies for achieving efficient light generation without relying on complex multi-emitter systems.
Over the course of the project, we demonstrated that polariton formation provides a viable pathway to selectively influence key emission processes in OLEDs. Importantly, our findings show that strong light–matter coupling does not universally enhance all radiative processes, but instead primarily affects inefficient recombination pathways and emission disperssion. This provides a realistic framework for using photonic design to suppress loss mechanisms and improve device operation. The project therefore concludes that polariton engineering represents a promising strategy for enhancing OLED performance while supporting the development of more stable and potentially lower-impact lighting technologies.
During the PLAS-OLED project, a comprehensive experimental and fabrication platform was established to enable the design, realization, and investigation of polariton OLEDs. We developed and implemented:
-An ultrahigh-vacuum deposition system for fabricating OLEDs integrated within optical microcavity architectures.
-An inert-environment characterization workflow ensuring reliable electrical and optical testing of sensitive devices.
-A combined ultrafast electro-optical excitation and spectroscopy setup providing direct access to the charge-to-photon conversion dynamics under electrical operation.
These capabilities enabled, for the first time, the direct investigation of electrically driven polariton OLEDs and their dynamical response. In parallel, the project developed a novel solution-based approach for fabricating high-quality distributed Bragg reflector (DBR) microcavities. This simplified previously complex fabrication routes and demonstrated that strong light–matter coupling can be achieved using scalable deposition methods compatible with lower-cost manufacturing. Using these tools, we successfully demonstrated polariton formation in OLED-relevant structures and gained detailed insight into the interaction between electrical excitation processes and cavity-modified emission.
The results of PLAS-OLED were disseminated through scientific publications and presentations at international conferences, contributing new experimental methodologies and conceptual understanding to the field of polariton optoelectronics. The fabrication techniques and experimental approaches developed during the project are now being further exploited in ongoing research into scalable polaritonic device architectures and energy-efficient lighting concepts.
-An ultrahigh-vacuum deposition system for fabricating OLEDs integrated within optical microcavity architectures.
-An inert-environment characterization workflow ensuring reliable electrical and optical testing of sensitive devices.
-A combined ultrafast electro-optical excitation and spectroscopy setup providing direct access to the charge-to-photon conversion dynamics under electrical operation.
These capabilities enabled, for the first time, the direct investigation of electrically driven polariton OLEDs and their dynamical response. In parallel, the project developed a novel solution-based approach for fabricating high-quality distributed Bragg reflector (DBR) microcavities. This simplified previously complex fabrication routes and demonstrated that strong light–matter coupling can be achieved using scalable deposition methods compatible with lower-cost manufacturing. Using these tools, we successfully demonstrated polariton formation in OLED-relevant structures and gained detailed insight into the interaction between electrical excitation processes and cavity-modified emission.
The results of PLAS-OLED were disseminated through scientific publications and presentations at international conferences, contributing new experimental methodologies and conceptual understanding to the field of polariton optoelectronics. The fabrication techniques and experimental approaches developed during the project are now being further exploited in ongoing research into scalable polaritonic device architectures and energy-efficient lighting concepts.
PLAS-OLED has advanced the understanding of how strong light–matter coupling influences OLED operation beyond previous expectations. Earlier assumptions in the field suggested that polariton formation could broadly accelerate emission processes and improve device efficiency. Our combined experimental and theoretical investigations instead reveal a more nuanced picture: strong coupling primarily impacts inefficient bimolecular recombination pathways, while already efficient radiative processes remain largely unaffected due to competitive dynamics.
This insight establishes a clearer strategy for using polaritonic effects to improve OLED performance — not by universally enhancing emission, but by selectively mitigating loss mechanisms. In addition, the project demonstrated that polaritons can be realised in solution-processed optical microcavities, representing a significant step toward scalable and less resource-intensive fabrication compared to traditional approaches.
Overall, PLAS-OLED moves polariton OLEDs from a conceptual research direction toward a practically informed design strategy for next-generation optoelectronic devices. The project provides both technological tools and fundamental understanding that define realistic pathways for integrating photonic engineering into future high-efficiency lighting systems.
This insight establishes a clearer strategy for using polaritonic effects to improve OLED performance — not by universally enhancing emission, but by selectively mitigating loss mechanisms. In addition, the project demonstrated that polaritons can be realised in solution-processed optical microcavities, representing a significant step toward scalable and less resource-intensive fabrication compared to traditional approaches.
Overall, PLAS-OLED moves polariton OLEDs from a conceptual research direction toward a practically informed design strategy for next-generation optoelectronic devices. The project provides both technological tools and fundamental understanding that define realistic pathways for integrating photonic engineering into future high-efficiency lighting systems.