Assessing Structural and Optical Properties of PTQ10-Based Donor Polymers in Solution for Eco-Friendly Photovoltaics:...

Area of Science:

• Materials Science
• Computational Chemistry
• Organic Electronics

Background:

• Aqueous-processable materials are key for eco-friendly organic solar cells (OSCs).
• Current green OSCs have lower efficiency compared to those processed with halogenated solvents.
• Polar side chains (SCs) enable aqueous solubility but impact device performance.

Purpose of the Study:

• To investigate the impact of alkyl and alkoxy side chains on PTQ10 polymer properties in solution.
• To understand how substituents affect structural and optical characteristics for OSC applications.
• To correlate molecular aggregation in solution with device performance.

Main Methods:

• Classical molecular dynamics simulations of oligomer chains at varying concentrations and solvents (water/ethanol, chloroform).
• Unsupervised machine learning and density functional theory (DFT) for quantum calculations and excited state analysis.
• Sequential Quantum Mechanics/Molecular Mechanics (QM/MM) approach to determine polymer absorption spectra.

Main Results:

• Simulations revealed polymer chain aggregation in solution at high concentrations.
• DFT calculations confirmed the influence of SCs on excited states.
• Experimental red shift in absorption spectra for PTQ(8bO2) in aqueous vs. chloroform mixtures validated simulation findings.
• Analysis of dimer models showed mixed spectral signatures due to electron-donating/accepting groups.

Conclusions:

• Side chain engineering significantly impacts polymer aggregation and optical properties in solution.
• Understanding solution-phase aggregation is critical for optimizing aqueous-processable OSCs.
• Computational methods combined with experimental data provide insights into structure-property relationships for green OSC development.