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Spin-Vibronic Intersystem Crossing and Molecular Packing Effects in Heavy Atom Free Organic Phosphor
Thomas Pope1, Julien Eng1, Andrew Monkman2
1Chemistry, School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne NE1 7RU, U.K.
This study reveals that HTANGO, a heavy metal-free organic molecule, achieves fast intersystem crossing (ISC) due to abundant triplet states. This mechanism explains its high efficiency as an organic room temperature phosphorescent (ORTP) dye.
Area of Science:
- Photochemistry
- Materials Science
- Quantum Chemistry
Background:
- HTANGO is a planar D3 symmetric azatriangulenetrione.
- It shows high solid-state phosphorescence quantum yield.
- It has potential as an organic room temperature phosphorescent (ORTP) dye.
Purpose of the Study:
- Investigate the excited state properties of HTANGO.
- Elucidate the mechanism of its high phosphorescence quantum yield.
- Understand the role of molecular alignment in solid-state emission.
Main Methods:
- Model linear vibronic coupling Hamiltonian.
- Quantum dynamics simulations.
- Quantum chemistry calculations on HTANGO dimer.
Main Results:
- Intersystem crossing (ISC) rate in HTANGO is ~10^10 s^-1.
- Fast ISC is facilitated by a high density of excited triplet states near singlet states.
- Rotational alignment of HTANGO dimers in the solid state is crucial for high phosphorescence.
Conclusions:
- HTANGO exhibits rapid ISC due to favorable excited state energetics.
- The molecular packing and orientation in the solid state significantly enhance phosphorescence efficiency.
- HTANGO is a promising candidate for heavy metal-free ORTP applications.
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