Effects of sub-wavelength photonic nanostructures on thermally-activated delayed fluorescence

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Organic light-emitting diodes (OLEDs) have become a dominant technology in the display industry and hold great promise for a variety of applications in the fields of lighting, visible communication, sensing and healthcare. Current research efforts focus on the development of thermally-activated delayed fluorescent (TADF) emitters that promise highly efficient and long-lifetime performance without the use of any heavy metals. These materials show a small energy gap between their singlet and triplet energy levels allowing the up-conversion of non-emissive triplets to light-emitting singlets at room temperature via the reverse intersystem crossing process. Although efficient triplet harvesting can take place in TADF OLEDs, the dynamics involved in the TADF mechanism need to be faster to substantially reduce the accumulation of long-lived triplet excitons during the device operation and improve their overall performance. This project addresses this research challenge by proposing an innovative approach based on the integration of sub-wavelength photonic nanostructures into TADF OLEDs. Via their effects on the local photonic density and the dielectric permittivity of the effective media, the photonic nanostructures will be engineered to accelerate both radiative decay and reverse intersystem crossing rates. This will improve the efficiency of OLEDs, especially at high brightness and increase their lifetime. The successful outcome of the project is expected to lead to an improvement of the TADF OLED technology and will be highly relevant for a range of other applications in fields as diverse as organic optoelectronics, sensing and photochemistry.