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

有机发光二极管(OLED)已成为显示行业的主导技术，在照明、可见光通信、传感和医疗保健等领域具有广阔的应用前景。目前的研究工作集中在开发热激活延迟荧光(TADF)发射器，这种发射器承诺在不使用任何重金属的情况下具有高效和长寿命的性能。这些材料在它们的单态和三态能级之间显示出很小的能隙，允许在室温下通过反向系统间交叉过程将非发射的三态上转换为发光的单态。虽然TADF OLED可以进行高效的三重态捕获，但TADF机制中涉及的动力学需要更快，以大幅减少器件运行过程中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创新的方法来解决这一研究挑战，该方法基于将亚波长光子纳米结构集成到TADF OLED中。通过它们对有效介质的局域光子密度和介电常数的影响，光子纳米结构将被设计成加速辐射衰减和系统间反向交叉的速率。这将提高OLED的效率，特别是在高亮度的情况下，并延长其寿命。该项目的成功成果预计将导致TADF OLED技术的改进，并将与有机光电子、传感和光化学等领域的一系列其他应用高度相关。

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.