Article

Breaking Kasha’s Rule as a Mechanism for Solution-Phase Room-Temperature Phosphorescence from High-Lying Triplet Excited State

Changfu FengInstitute of Molecule Plus, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, P. R. ChinaShuai LiInstitute of Molecule Plus, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, P. R. ChinaLiyuan FuBeijing Key Laboratory for Optical Materials and Photonic Devices, Department of Chemistry, Capital Normal University, Beijing 100048, P. R. ChinaXiaoxiao XiaoBeijing Key Laboratory for Optical Materials and Photonic Devices, Department of Chemistry, Capital Normal University, Beijing 100048, P. R. ChinaZhenzhen XuBeijing Key Laboratory for Optical Materials and Photonic Devices, Department of Chemistry, Capital Normal University, Beijing 100048, P. R. ChinaQing LiaoBeijing Key Laboratory for Optical Materials and Photonic Devices, Department of Chemistry, Capital Normal University, Beijing 100048, P. R. ChinaYishi WuBeijing Key Laboratory for Optical Materials and Photonic Devices, Department of Chemistry, Capital Normal University, Beijing 100048, P. R. ChinaJiannian YaoInstitute of Molecule Plus, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, P. R. ChinaHongbing FuBeijing Key Laboratory for Optical Materials and Photonic Devices, Department of Chemistry, Capital Normal University, Beijing 100048, P. R. China

2020en

ABI

Abstract

Organic room-temperature phosphorescence (ORTP) has been demonstrated successfully in solids. In contrast, solution-phase ORTP is rarely achieved, because the T1 → S0 phosphorescence is too slow to compete against nonradiative decay and the oxygen-quenching effect. Here, we reported that suppression of Kasha’s rule is a strategy to achieve solution-phase ORTP from the high-lying T2 state by spatially separating T2 and T1 on different parts of the molecule (CzCbDBT) composed of carbonyl (Cb), dibenzothiophene (DBT), and carbazole moiety (Cz). On one hand, intersystem crossing (ISC) is much faster from S1 to T2 than that to T1, owing to the small energy-gap ΔES1–T2 and large spin–orbital coupling ξS1–T2. On the other hand, T2 → T1 internal conversion is inhibited owing to spatial separation, i.e., T2 on CbDBT and T1 on Cz, respectively. Also, combination of very fast radiative decay from T2 to S0 owing to large ξT2–S0, the efficient solution-phase ORTP emission from the T2 state was finally achieved.

Identifiers

DOI: 10.1021/acs.jpclett.0c02180

Citations and references

Cited by 20 references

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