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Environmental effects on the singlet fission phenomenon: a model Hamiltonian-based study
Pablo Roseiro1, Vincent Robert1
1Laboratoire de Chimie Quantique, UMR 7177 Université de Strasbourg CNRS, 4 rue Blaise Pascal, 67000, Strasbourg, France. vrobert@unistra.fr.
Physical Chemistry Chemical Physics : PCCP
|June 22, 2022
Summary
The spin state of a molecule's environment significantly impacts its potential for singlet fission. This study shows that a triplet environment enhances singlet fission more than a singlet environment.
Area of Science:
- Photochemistry
- Quantum Chemistry
- Materials Science
Background:
- Singlet fission is a process where one high-energy singlet exciton splits into two lower-energy triplet excitons.
- The efficiency of singlet fission is governed by thermodynamic rules, particularly the relative energies of the electronic states.
- Understanding the influence of the molecular environment is crucial for designing efficient singlet fission materials.
Purpose of the Study:
- To investigate the effect of the molecular environment's spin state on the energetics of singlet fission.
- To determine how embedding a chromophore influences the energy differences critical for singlet fission.
- To explore the role of the environment's electronic structure in modulating singlet fission propensity.
Main Methods:
- Development of a model Hamiltonian based on local spin states of a chromophore and its environment.
- Calculation of relative energies of singlet (S0, S1) and triplet (T1) states.
- Comparison of energy ratios for free chromophores versus embedded chromophores in singlet and triplet environments.
Main Results:
- Embedding a chromophore in a singlet environment increases the critical ratio for singlet fission by up to 6% compared to a free chromophore.
- Modifying the electronic structure of the singlet environment further alters singlet fission propensity.
- A triplet environment enhances singlet fission propensity by approximately 10% compared to a singlet environment.
- The model suggests that embedding can reverse spin state ordering under certain conditions.
Conclusions:
- The spin nature of the molecular environment is a critical factor in identifying potential singlet fission candidates.
- Environmental effects, including spin state and electronic structure, significantly influence spectroscopic properties and energy transfer processes.
- This model provides a simplified yet powerful framework for understanding and predicting singlet fission behavior.
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