Cyanobenzene-Modified Quinoxaline-Based Acceptors with Optimal Excitonic Behavior Enable Efficient Organic Solar...

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Cyanogroup (-CN) functionalization is key for optimizing small-molecule acceptors (SMAs) in organic solar cells (OSCs) due to its electron-withdrawing and polar nature.
• Strategic placement of functional groups is crucial for tuning the electronic and photophysical properties of SMAs.

Purpose of the Study:

• To synthesize and investigate novel SMAs with cyanobenzene substitution in the central core.
• To explore the impact of asymmetric versus symmetric cyanobenzene substitution on molecular properties and device performance.
• To understand the mechanisms behind performance enhancement in OSCs utilizing these novel SMAs.

Main Methods:

• Synthesis of four novel SMAs: phCN-F, phCN-Cl, 2phCN-F, and 2phCN-Cl, featuring cyanobenzene substitution.
• Theoretical and experimental analyses to evaluate excitonic properties, molecular packing, and phase separation.
• Fabrication and testing of organic solar cell devices to assess performance and thermal stability.

Main Results:

• Asymmetric cyanobenzene substitution significantly influences molecular packing and phase separation, improving exciton dissociation, charge transport, and extraction.
• The phCN-F based OSC achieved a record power conversion efficiency of 20.16%, outperforming symmetrically substituted counterparts.
• Devices utilizing phCN-F demonstrated excellent thermal stability, retaining over 90% efficiency after 3000 hours at 85°C.

Conclusions:

• Asymmetric cyanobenzene substitution in the central core is a promising strategy for designing high-performance SMAs.
• This approach offers valuable insights into optimizing molecular design for record-breaking efficiencies and enhanced stability in organic solar cells.
• The findings pave the way for developing next-generation organic photovoltaic materials.