Excimer formation dynamics in the isolated tetracene dimer.

Area of Science:

• Physical Chemistry
• Materials Science
• Organic Electronics

Background:

• Excimer formation and singlet-correlated triplet pair states (¹(TT)) are vital for organic electronics.
• Understanding these dynamics is key to developing efficient organic electronic devices.

Purpose of the Study:

• To investigate the photoinduced dynamics of excimer formation in tetracene dimers.
• To gain mechanistic insight into excimer formation dynamics and its interplay with ¹(TT) states.

Main Methods:

• Time-resolved photoionization and photoion imaging experiments.
• Picosecond laser excitation into the S₂ state.
• Quantum-classical photodynamics simulations (CISD and TD-lc-DFTB methods).

Main Results:

• Biexponential time dependence observed (≈10 ps to 100 ps) attributed to excimer relaxation and ground state deactivation.
• Simulations identified a dominant pathway forming a perfectly stacked excimer.
• A secondary relaxation channel to a less stable dimer conformation was uncovered.
• Electronic and geometric relaxation to the excimer state completed in <10 ps.
• Transient population of the ¹(TT) state observed, depopulating within 8 ps.

Conclusions:

• Excimer formation in tetracene dimers involves distinct relaxation pathways.
• The singlet-correlated triplet pair state is transiently populated during relaxation.
• These findings provide crucial mechanistic insights for designing efficient organic electronic materials.