Low-Lying Excited States in Thiophene-Based Cyclic Molecule Suitable for Optoelectronics: A Density Matrix...

Area of Science:

• Organic electronics
• Photophysics
• Materials science

Background:

• Thiophene-based cyclic oligomers are explored for advanced electronic applications.
• Understanding excited states is crucial for material design.

Purpose of the Study:

• Investigate the low-lying excited states of tetrathia[22]annulene (TTA).
• Evaluate TTA's potential for solar energy harvesting and singlet fission.
• Assess the impact of donor-acceptor substitution on TTA's properties.

Main Methods:

• Density matrix renormalization group technique.
• Long-range Pariser-Parr-Pople (PPP) model Hamiltonian.

Main Results:

• Calculated S₁ optical gap of 1.76 eV for TTA, closely matching experimental values (1.6 eV).
• Identified promising diradical character and a low T₁/S₁ ratio (0.12) for singlet fission.
• Donor-acceptor substitution reduced the optical gap to 1.35 eV.

Conclusions:

• TTA is a promising material for harvesting visible to near-infrared solar light.
• TTA demonstrates potential as a singlet fission material.
• (D-A)-substituted TTA is suitable for organic light-emitting devices.