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

有机发光二极管（OLED）已成为显示器行业的主导技术，并在照明、可视通信、传感和医疗保健领域的各种应用中具有很大的前景。目前的研究工作集中在开发热激活延迟荧光（TADF）发射器，承诺高效和长寿命的性能，而不使用任何重金属。这些材料显示出它们的单重态和三重态能级之间的小能隙，允许在室温下通过反向系间交叉过程将非发射三重态上转换为发光单重态。虽然在TADF OLED中可以发生有效的三重态收获，但TADF机制中涉及的动力学需要更快，以大幅减少器件操作期间长寿命三重态激子的积累并提高其整体性能。该项目通过提出一种基于将亚波长光子纳米结构集成到TADF OLED中的创新方法来解决这一研究挑战。通过它们对有效介质的局部光子密度和介电常数的影响，光子纳米结构将被设计为加速辐射衰减和反向系统间交叉速率。这将提高OLED的效率，特别是在高亮度下，并延长其寿命。该项目的成功结果预计将导致TADF OLED技术的改进，并将与有机光电子学，传感和光化学等领域的其他应用高度相关。

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.