The Demonstration of a Multiply Noncovalently Assembled Dimeric Acceptor Enabling Organic Solar Cells Approaching 21%...

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Organic solar cells (OSCs) show promise but face challenges with molecular ordering and high exciton binding energies.
• Small molecule acceptors (SMAs) are crucial components in OSCs, influencing device performance.

Purpose of the Study:

• To design and synthesize novel SMAs by tuning sulfur atom content to improve molecular ordering and reduce exciton binding energy.
• To investigate the impact of intermolecular noncovalent interactions on the self-assembly and properties of SMAs.

Main Methods:

• Synthesis of four SMA derivatives (CHSMe, CHSPh, CH2SPh, CHDF) with varying sulfur atom numbers.
• Single-crystal X-ray diffraction to analyze molecular structure and intermolecular interactions (C-H···S, C═S···S).
• Fabrication and characterization of OSC devices using the developed SMAs paired with PM6.

Main Results:

• Designed SMAs exhibit strong intermolecular C-H···S and C═S···S noncovalent interactions, forming bimolecular structure units.
• CHDF demonstrated a nearly coplanar dimer formation in single crystals due to dual hydrogen-bonding and C═S···S interactions.
• CHDF showed enhanced crystallinity, extensive π-π stacking, and a reduced exciton binding energy of 150 meV.
• CHDF-based OSCs achieved a champion power conversion efficiency of 20.69% with PM6.

Conclusions:

• Tuning sulfur atom content in SMAs effectively promotes bimolecular self-assembly through specific noncovalent interactions.
• Enhanced molecular ordering and reduced exciton binding energy in SMAs lead to significant improvements in OSC performance.
• The developed CHDF material represents a high-performance acceptor for binary organic solar cells.