Exploring excited state dynamics in benzocarbazole derivatives through transient absorption spectroscopy

被引:1
作者
Yang, Yonggang [1 ]
Du, Mengru [1 ]
Liu, Yang [1 ]
Qin, Chaochao [1 ]
Zhuang, Chunsheng [2 ]
Liu, Yufang [1 ,2 ]
机构
[1] Henan Normal Univ, Sch Phys, Henan Key Lab Infrared Mat & Spectrum Measures & A, Xinxiang 453007, Peoples R China
[2] Inst Appl Phys, Henan Acad Sci, Zhengzhou 450008, Peoples R China
基金
中国国家自然科学基金;
关键词
Pure organic room-temperature phosphorescent; Transient absorption spectroscopy; Heteroatom effect; Intersystem crossing; Internal conversion; ROOM-TEMPERATURE PHOSPHORESCENCE; ACHIEVING PERSISTENT; HOST MATERIALS; BASIS-SETS; PHENYLCARBAZOLE; TRIPHENYLAMINE; EFFICIENCY; AFTERGLOW; MOLECULE; DESIGN;
D O I
10.1016/j.jlumin.2024.120864
中图分类号
O43 [光学];
学科分类号
070207 ; 0803 ;
摘要
Increasing the spin-orbit coupling (SOC) constant by introducing heteroatoms is crucial approach for achieving efficient pure organic room-temperature phosphorescent (RTP). This research focused on the molecules 3,3 ''-Di(9H-carbazol-9-yl)-1,1':3 ',1 ''-terphenyl (DCzTp) and 2,6-Bis[3-(9H-carbazol-9-yl)phenyl]pyridine (DCzPPy) using transient absorption spectroscopy experiments. For DCzTp, the femtosecond spectroscopy revealed an excited state absorption (ESA) signal at 630 nm, which reached a maximum within 1.3 ps, followed by decay of the ESA signal and appearance of triplet-triplet absorption (TTA) signal at 405 nm. An isosbestic point at 465 nm indicated the presence of intersystem crossing (ISC). In nanosecond spectroscopy, the TTA signal reached its maximum within 23 ns, and then the triplet state lifetime (tau(TTA)) decayed within 1.9 mu s. DCzPPy exhibited faster ISC lifetime (tau(ISC) = 5.5 ns) and longer tau(TTA) (4.9 mu s) compared to DCzTp. Theoretical simulations demonstrated that DCzTp transitions from the lowest singlet excited state (S-1) to the lowest triplet excited state, while DCzPPy transitions from S-1 to the higher triplet excited state (T-2). Notably, due to the heteroatom effect, the SOC constant of DCzPPy (0.27 cm(-1)) was greater than that of DCzTp (0.23 cm(-1)), leading to a faster tau(ISC) (5.5 ns vs. 11.4 ns). Additionally, DCzPPy exhibited an additional triplet state internal conversion process (1.1 mu s), leading to a longer tau(TTA) (4.9 mu s vs. 1.9 mu s). This research provides valuable insights into how heteroatoms enhance RTP efficiency in pure organic molecules.
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页数:8
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