Investigation into aggregation types in a benzodithiophene-isoindigo copolymer

Area of Science:

• Materials Science
• Polymer Chemistry
• Organic Electronics

Background:

• The aggregation behavior of conjugated polymers is crucial for their optoelectronic properties.
• H-type aggregates are optimal for solar cells, while J-type aggregates are preferred for light-emitting diodes.

Purpose of the Study:

• To determine the aggregation types present in a benzodithiophene-isoindigo-based (PBDTI-DT) copolymer.
• To correlate aggregation type with potential applications in electronic devices.

Main Methods:

• Utilized Huang-Rhys factor evolution with temperature.
• Performed Franck-Condon analysis.
• Calculated relative quantum yield (QY).
• Employed time-dependent density functional theory (TD-DFT) for spectral analysis.

Main Results:

• All three experimental methods indicated the presence of both H-type and J-type aggregates.
• Relative quantum yield calculations demonstrated that H-aggregates are more dominant in the PBDTI-DT copolymer.
• TD-DFT identified two absorption bands attributed to local π - π* and intramolecular charge-transfer transitions.

Conclusions:

• The PBDTI-DT copolymer exhibits a mix of aggregation types, with a predominance of H-aggregates.
• The findings suggest potential for PBDTI-DT in solar cell applications due to dominant H-aggregation.