Hot-Casting Strategy Empowers High-Boiling Solvent-Processed Organic Solar Cells with Over 18.5% Efficiency

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Organic solar cells (OSCs) often rely on chloroform, a volatile halogenated solvent, limiting their processing window.
• Developing OSCs with high-boiling point solvents is crucial for wider applicability and improved performance.

Purpose of the Study:

• To investigate a hot-casting strategy for preparing OSC active layers using high-boiling solvents.
• To enhance the performance and processing window of organic solar cells.

Main Methods:

• Utilized high-boiling solvents: chlorobenzene (CB) and ortho-xylene (OX).
• Employed a hot-casting technique for active layer preparation.
• Conducted in situ tests and morphological characterization.
• Fabricated OSC devices using PM6:BO-4Cl and PM6:BTP-eC9 active layers.

Main Results:

• Hot-casting facilitated fast, synchronous molecular assembly of donor and acceptor materials.
• Achieved improved donor/acceptor ratio, vertical phase separation, and molecular stacking.
• OSCs processed with hot-casting in CB and OX reached efficiencies of 18.03% and 18.12% (PM6:BO-4Cl), respectively.
• OSCs with PM6:BTP-eC9 in OX achieved a record fill factor of 80.31% and efficiency of 18.52% for binary green solvent devices.

Conclusions:

• The hot-casting strategy effectively enhances molecular arrangement and device performance in OSCs.
• This method offers a facile route to boost OSC efficiency using high-boiling solvents, including green solvents like OX.
• The findings present a promising approach for scalable and efficient OSC fabrication.