Fine Modulation of the Higher-Order Excitonic States Towards More Efficient Conversion from Upper Level Triplet to Singlet.
Fine Modulation of the Higher-Order Excitonic States Towards More Efficient Conversion from Upper Level Triplet to Singlet.
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DOI：
10.1021/acs.jpclett.9b02751
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发表时间：
2019-10
期刊：
影响因子：
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通讯作者：
Yuwei Xu;Cong Wang;Xuehong Zhou;Jiadong Zhou;Xiaomin Guo;Xiaoming Liang;Dehua Hu;Feng Li;Dongge Ma;Yuguang Ma
中科院分区：
文献类型：
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作者：
Yuwei Xu;Cong Wang;Xuehong Zhou;Jiadong Zhou;Xiaomin Guo;Xiaoming Liang;Dehua Hu;Feng Li;Dongge Ma;Yuguang Ma
热激子发光体能够通过从高阶三重态(HRISC)到单重态(Singlet)的系统间反向交叉来获得非发射的三重态激子，在高效有机荧光发光二极管(OLED)方面具有巨大的潜力。尽管自旋-轨道耦合(SOC)被认为是影响RISC过程的关键因素，但其对热激子材料的影响却鲜有研究。在这里，我们设计并合成了两种蓝色发光的热激子发光体PABP和PAIDO，通过对激发态性质的调制来研究这一问题。理论和实验研究表明，PAIDO的S_1(π-π~*)和T_n(T_3，n-π~*)之间的SOC越强，与PABP相比，hRISC越快、效率越高，从而获得更高的外量子效率和激子利用效率。实验测得的热激子材料的hRISC速率(K_HRISC)约为10~(-7)S~(-1)，比热激活的延迟荧光材料快得多。
Hot exciton luminogens capable of harvesting non-emissive triplet excitons via reverse intersystem crossing from high-order triplet (hRISC) to singlet have great potential in high-efficiency fluorescent organic light-emitting diodes (OLEDs). Although spin-orbit coupling (SOC) is regarded as a key factor affecting the RISC process, its effects on hot exciton materials are poorly studied. Herein, we design and synthesize two blue-emitting hot exciton luminogens, PABP and PAIDO, to study this issue by modulating the excited state properties. Theoretical and experimental researches demonstrate that a stronger SOC between energetically close S1 (π-π*) and Tn (T3, n-π*) of PAIDO gives rise to faster and more efficient hRISC versus PABP leading to a higher external quantum efficiency and a higher exciton utilization efficiency. Crucially, the experimentally measured hRISC rate (k_hRISC) of hot exciton materials is on the order of 107 S-1, which is much faster than the thermally activated delayed fluorescence materials.