Electronic energy migration in solid versus liquid host matrices for concentrated perylenediimide dye solutions

Area of Science:

• Photophysics and exciton dynamics
• Materials science of disordered systems

Background:

• Exciton diffusion is crucial for energy transfer in materials.
• Understanding exciton motion in disordered environments is key to developing new optoelectronic devices.
• Forster-type theories provide a framework for modeling exciton diffusion.

Purpose of the Study:

• To evaluate Forster-type theories of exciton diffusion in disordered environments.
• To compare exciton energy transfer rates in liquid and solid matrices.
• To investigate the influence of molecular translation and energetic averaging on exciton motion.

Main Methods:

• Time-resolved fluorescence decays were measured for Lumogen Red donor molecules in CHCl(3) and dimethylformamide.
• Energy transfer to Rhodamine 700 acceptor molecules was quantified.
• Exciton motion was studied over a range of Lumogen Red concentrations (1 × 10(-4) to 5 × 10(-2) M).
• Results were compared to previous studies on exciton diffusion in solid poly(methyl methacrylate) (PMMA).

Main Results:

• Exciton energy migration in liquids was found to be 2-3 times faster than in solid PMMA.
• Diffusion constants in liquids ranged from 2.2 to 3.1 nm(2)/ns, compared to 1.1-1.2 nm(2)/ns in solid PMMA.
• Liquid results agreed well with theoretical predictions, while solid PMMA results were significantly slower.

Conclusions:

• Liquid environments facilitate faster exciton energy migration due to rapid energetic averaging.
• Solid matrices like PMMA exhibit slower exciton diffusion due to static disorder and trapped configurations.
• The findings highlight the importance of environmental dynamics in controlling exciton transport.