Relating Chromophoric and Structural Disorder in Conjugated Polymers

Area of Science:

• Materials Science
• Polymer Chemistry
• Computational Chemistry

Background:

• Amorphous conjugated polymers' optoelectronic properties depend on conformational disorder.
• Spectroscopy characterizes light-interacting polymer chain fragments (chromophores).
• Interpreting spectroscopic signatures of polymer conformation presents theoretical challenges.

Purpose of the Study:

• Investigate the link between optical gaps, excited states, and chromophore structure in poly(3-hexyl)-thiophene (P3HT).
• Utilize quantum-classical atomistic simulations to understand structure-property relationships.
• Explain the spectral behavior of P3HT, particularly its red-shifted absorption with increasing temperature.

Main Methods:

• Quantum-classical atomistic simulations.
• Analysis of ground-state optical gaps and excited-state properties.
• Correlation of spectroscopic data with structural features of P3HT chromophores.

Main Results:

• Chromophoric disorder in P3HT arises from excited-state delocalization and electron-hole polarization.
• Torsional disorder, influenced by side chains, controls this interplay.
• Predicted and explained the counterintuitive red-shifted absorption of P3HT with chromophore shortening at higher temperatures.

Conclusions:

• Established a conceptual framework linking structural disorder to spectral behavior in amorphous conjugated polymers.
• Introduced the concept of disorder-induced separation of charges in these materials.
• Provided insights into the fundamental optoelectronic properties of P3HT.