Mac Ciarnáin Rossa, Mo Hin Wai, Nagayoshi Kaori, Fujimoto Hiroshi, Harada Kentaro, Gehlhaar Robert, Ke Tung Huei, Heremans Paul, Adachi Chihaya
imec, Kapeldreef 75, Leuven, B3001, Belgium.
KU Leuven, Kasteelpark Arenberg 10, Leuven, B3001, Belgium.
Adv Mater. 2022 Jul;34(29):e2201409. doi: 10.1002/adma.202201409. Epub 2022 Jun 12.
Device optimization of light-emitting diodes (LEDs) targets the most efficient conversion of electrically injected charges into emitted light. The emission zone in an LED is where charges recombine and light is emitted from. It is believed that the emission zone is strongly linked to device efficiency and lifetime. However, the emission zone size is below the optical diffraction limit, so it is difficult to measure. An accessible method based on a single emission spectrum that enables emission zone measurements with sub-second time resolution is shown. A procedure is introduced to study and control the emission zone of an LED system and correlate it with device performance. A thermally activated delayed fluorescence organic LED emission zone is experimentally measured over all luminescing current densities, while varying the device structure and while ageing. The emission zone is shown to be finely controlled by emitter doping because electron transport via the emitter is the charge-transport bottleneck of the system. Suspected quenching/degradation mechanisms are linked with the emission zone changes, device structure variation, and ageing. Using these findings, a device with an ultralong 4500 h T lifetime at 1000 cd m with 20% external quantum efficiency is shown.
发光二极管（LED）的器件优化旨在将电注入电荷最有效地转换为发射光。LED中的发射区是电荷复合并发射光的地方。据信，发射区与器件效率和寿命密切相关。然而，发射区尺寸低于光学衍射极限，因此难以测量。本文展示了一种基于单发射光谱的可及方法，该方法能够以亚秒级时间分辨率进行发射区测量。引入了一种程序来研究和控制LED系统的发射区，并将其与器件性能相关联。在所有发光电流密度下，在改变器件结构和老化的同时，通过实验测量了热激活延迟荧光有机LED的发射区。结果表明，发射区可通过发射体掺杂进行精细控制，因为通过发射体的电子传输是系统的电荷传输瓶颈。疑似的猝灭/降解机制与发射区变化、器件结构变化和老化有关。利用这些发现，展示了一种在1000 cd/m²下具有4500小时超长T寿命且外量子效率为20%的器件。
