Zhou Zeyang, Chang Qingda, Chen Rui, Jin Pengfei, Yin Baipeng, Zhang Chuang, Yao Jiannian
Key Laboratory of Photochemistry, Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
University of Chinese, Academy of Sciences, Beijing 100049, China.
Phys Chem Chem Phys. 2024 Sep 25;26(37):24498-24505. doi: 10.1039/d4cp02801e.
Light-emitting electrochemical cells (LECs) are appealing for cost-effective, large-area emission applications; however, their luminescence efficiency is significantly limited by exciton annihilation caused by high concentration polarons. Here, we present thermally activated delayed fluorescence (TADF) sensitized fluorescence LECs (TSF-LECs) that achieve a record 9% EQE. The TADF sensitizers with rapid reverse intersystem crossing (RISC) rates can effectively convert triplet excitons to singlet excitons in LECs, thereby establishing a more efficient overall energy transfer pathway. Importantly, magneto-electroluminescence measurements indicate that the additional RISC route in TSF-LECs significantly suppresses the annihilation of triplet excitons and thus reduces exciton loss under high concentration polaron conditions. Compared to LECs without a sensitizer, TSF-LECs exhibit improved EQE and luminance, extended operational lifetimes, and suppressed efficiency roll-off. A flexible display prototype based on TSF-LECs was further fabricated, capable of stably displaying high-brightness preset patterns for extended periods. The exploration of the exciton dynamics in high concentration polaron environments offers valuable insights for future developments in high-efficiency LEC technology.
发光电化学电池（LEC）因其具有成本效益且适用于大面积发光应用而备受关注；然而，其发光效率受到高浓度极化子引起的激子湮灭的显著限制。在此，我们展示了热激活延迟荧光（TADF）敏化荧光LEC（TSF-LEC），其外量子效率（EQE）达到了创纪录的9%。具有快速反向系间窜越（RISC）速率的TADF敏化剂能够在LEC中有效地将三重态激子转化为单重态激子，从而建立更高效的整体能量转移途径。重要的是，磁电致发光测量表明，TSF-LEC中的额外RISC途径显著抑制了三重态激子的湮灭，从而减少了高浓度极化子条件下的激子损失。与没有敏化剂的LEC相比，TSF-LEC表现出更高的EQE和亮度、更长的工作寿命以及抑制的效率滚降。基于TSF-LEC的柔性显示原型进一步被制造出来，能够长时间稳定显示高亮度预设图案。对高浓度极化子环境中激子动力学的探索为高效LEC技术的未来发展提供了有价值的见解。
