High-Performance CH-Series Non-Fullerene Acceptors for Organic Photovoltaics

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Organic solar cells (OSCs) utilizing non-fullerene acceptors (NFAs) have achieved high power conversion efficiencies (PCEs) exceeding 21%.
• However, OSCs still lag behind inorganic photovoltaics due to significant nonradiative recombination energy losses (over 0.2 eV) stemming from material properties like flexible frameworks and large exciton binding energies.
• Overcoming these losses requires multiscale regulation of molecular properties and aggregation behaviors.

Purpose of the Study:

• To review the development of electron acceptor materials, focusing on high-efficiency NFAs like Y6 analogs.
• To introduce novel CH-series NFAs with an "acceptor-donor-acceptor" architecture designed to overcome limitations in current acceptor designs.
• To explore strategies for further improving OSC performance through molecular design and novel photoelectric conversion mechanisms.

Main Methods:

• Development of CH-series NFAs featuring multi-functionalized central units and an "acceptor-donor-acceptor" structure.
• Analysis of CH-series NFA advantages, including induction of favorable molecular packing via weak intermolecular interactions (e.g., F-H, S, π bonds).
• Construction of rigid central-unit-linked dimeric/trimeric NFAs with multiple free terminals to enhance intermolecular packing.

Main Results:

• CH-series NFAs promote multidimensional long-range ordered molecular stacking, minimizing energy loss pathways.
• The novel design overcomes limitations of traditional acceptor architectures, enhancing intermolecular packing.
• Binary OSCs based on CH-series NFAs have achieved PCEs approaching 21%, demonstrating their high performance.

Conclusions:

• CH-series NFAs represent a versatile platform for developing OSCs with record-breaking PCEs due to their structural tunability.
• Future directions include optimizing molecular structure and packing to reduce exciton binding energies and exploring new photoelectric mechanisms (e.g., triplet excitons, singlet fission).
• Extending NFA absorption to the near-infrared II region and applying these strategies could significantly reduce the PCE gap with inorganic photovoltaics.