CF₃-Functionalized Side Chains in Nonfullerene Acceptors Promote Electrostatic Interactions for Highly Efficient...

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Next-generation nonfullerene acceptors (NFAs) are crucial for advancing organic solar cells (OSCs).
• Existing NFAs, like Y6, have driven progress, but further optimization is needed.

Purpose of the Study:

• To design and characterize a new series of NFAs with CF3-terminated side chains of varying linker lengths.
• To investigate the impact of these side chains on intermolecular interactions, crystal structure, and photovoltaic performance.
• To compare the performance of these new NFAs against the established Y6 acceptor.

Main Methods:

• Synthesis of NFAs with CF3-terminated side chains (n=1, 2, 3).
• Single-crystal X-ray diffraction for structural analysis.
• Comprehensive photovoltaic characterization, including efficiency, fill-factor, and charge mobility measurements.
• Comparison with Y6-based organic solar cells.

Main Results:

• NFAs with CF3-terminated side chains exhibited unusual 2D mesh-like crystal structures with strong intermolecular interactions.
• These structural features led to enhanced charge mobility and improved photovoltaic performance.
• Varying CF3-terminated side chain linker lengths modulated light harvesting, charge recombination, and the photovoltaic bandgap.
• The NFA with a CF3-(CH2)2-CF3 linker achieved a power conversion efficiency of 19.08% and a fill-factor of 80.09%.

Conclusions:

• CF3-terminated side chains are effective in designing high-performance NFAs for organic solar cells.
• The CF3-(CH2)2-CF3 based NFA demonstrates superior and balanced photovoltaic metrics.
• This approach offers a promising strategy for accelerating the development of next-generation organic solar cells.