Bulk Heterojunction Morphologies with Atomistic Resolution from Coarse-Grain Solvent Evaporation Simulations

Area of Science:

• Materials Science
• Computational Chemistry
• Renewable Energy

Background:

• Optimizing morphology in bulk heterojunction (BHJ) organic solar cells is crucial for high efficiency.
• Predicting morphologies for new donor-acceptor blends remains a significant challenge.
• Existing methods struggle to balance scale, chemical detail, and experimental relevance for high-throughput screening.

Purpose of the Study:

• To propose a novel computational method for generating atom-resolved BHJ morphologies.
• To enable the rational design of new materials for organic solar cells.
• To facilitate high-throughput screening of material combinations for optimal device performance.

Main Methods:

• Utilized coarse-grain (CG) molecular dynamics simulations to model large-scale morphological organization during solution-processing.
• Employed CG models that retain chemical specificity for direct material design.
• Implemented backmapping to retrieve fully atomistic detail for advanced calculations.

Main Results:

• Successfully predicted morphologies for the poly(3-hexyl-thiophene) (P3HT)-phenyl-C61-butyric acid methyl ester (PCBM) blend, matching experimental data.
• Investigated the impact of drying rate, P3HT molecular weight, and thermal annealing, observing trends consistent with experimental findings.
• Demonstrated the method's ability to reduce the parameter space for optimizing BHJ morphologies.

Conclusions:

• The proposed simulation methodology accurately predicts BHJ morphologies and guides material design.
• This approach is applicable to optimizing various solution-processed soft matter devices beyond organic solar cells.
• Facilitates faster development cycles for high-performance organic electronic materials.