Crystalline and Amorphous Interface Simulations of Donor-Acceptor Blends.

Area of Science:

• Materials Science
• Computational Chemistry
• Organic Electronics

Background:

• Organic solar cell performance relies on morphology, controlling exciton dissociation and charge transport.
• Blend miscibility and processing are critical factors in achieving optimal nanoscale morphology.

Purpose of the Study:

• To investigate the blend miscibility of P3HT and O-IDTBR using a "push-pull" computational technique.
• To explore the impact of this miscibility on the nanoscale morphology of organic solar cells.

Main Methods:

• Utilized a "push-pull" computational technique to determine the Flory-Huggins χ parameter.
• Employed virtual site coarse-graining simulations for large systems (30 nm) and long timescales (10 μs) to model equilibrated morphology.

Main Results:

• The P3HT:O-IDTBR blend exhibits UCST behavior, with miscibility primarily driven by enthalpy.
• Amorphous phase separation shows O-IDTBR swelling P3HT but not percolating.
• Crystallinity significantly affects the interface: amorphous interfaces are wide, while crystalline interfaces are sharp and ordered.

Conclusions:

• Wide amorphous interfaces offer diverse donor-acceptor contacts but hinder charge transport due to lack of percolation.
• Sharp crystalline interfaces, though fewer in contact, facilitate efficient charge separation due to ordered domains.