Theoretical Study on Singlet Fission Dynamics and Triplet Migration Process in Symmetric Heterotrimer Models

Area of Science:

• Photophysical processes
• Organic electronics
• Materials science

Background:

• Singlet fission (SF) is a key process for enhancing solar cell efficiency.
• Understanding exciton dynamics is crucial for designing efficient organic electronic materials.
• Directional triplet exciton migration is desirable for advanced optoelectronic applications.

Purpose of the Study:

• To establish design principles for controlling triplet exciton migration via singlet fission.
• To investigate the influence of substituents on SF dynamics in heterotrimer systems.
• To explore the potential of heterotrimers for enhanced SF selectivity.

Main Methods:

• Time-dependent density functional theory (TDDFT) calculations.
• Analysis of substituent effects using Hammett's para-substitution coefficients (σp).
• Quantum dynamics simulations and electronic coupling calculations.

Main Results:

• Substituent induction effects correlate with S1, T1, HOMO, and LUMO energy levels.
• Heterotrimers show over 70% increased selectivity for spatially separated triplet-triplet (TT) states compared to homotrimers.
• An optimal difference in σp between terminal and central monomers was identified for increased SF rates.

Conclusions:

• Structural asymmetry in heterotrimers, driven by substituent effects, enhances SF rates through quantum interference.
• This work provides a pathway for engineering directional triplet migration in organic materials.
• The findings offer valuable insights for the development of next-generation solar cells and optoelectronic devices.