Afterglow OLEDs incorporating bright closely stacked molecular dimers with ultra-long thermally activated delayed fluorescence

作者：Qiu, Weidon; Liu, Denghu; Chen, Zijian; Gan, Yiyang; Xiao, Shu; Peng, Xiaomei; Zhang, Difei; Cai, Xinyi; Li, Mengke; Xie, Wentao; Sun, Guanwei; Jiao, Yihang; Gu, Qing; Ma, Dongge; Su, Shi-Jian^*

来源：Matter, 2023, 6(4): 1231-1248.

DOI：10.1016/j.matt.2023.02.002

• LIGHT-EMITTING-DIODES
• PI-PI
• BLUE
• EMISSION
• EFFICIENCY
• CRYSTAL
• RING

Purely organic luminescent materials exhibiting afterglow emission after photoexcitation have been developed recently and hold great promise for future applications, whereas the afterglow from electro-excitation remains rare and inefficient. Here, afterglow electrolumi-nescence is achieved based on an organic dimer system with high photoluminescence quantum yield and unprecedented long-lived thermally activated delayed fluorescence (TADF) characteristics. The strong p -p interactions and aggregation structures can sup-press nonradiative transition and promote fluorescence emission. In addition, the molecular stacking also renders a moderate singlet-triplet energy gap, enabling a long-lived TADF afterglow. In combination with host-guest interaction optimization, efficient organic light-emitting diodes (OLEDs) based on the dimer system achieve high external quantum efficiency of 14.7% along with bright afterglow emission with lifetime of 157 ms. This work not only extends the scope of purely organic aggregates for novel optoelec-tronic properties and applications but also opens up new pathways for achieving efficient afterglow OLEDs with TADF mechanism.