Remote Modification-Induced Butterfly Effect on Nonfullerene Acceptor Aggregation for Efficient Organic Solar Cells

Area of Science:

• Materials Science
• Photovoltaics
• Organic Electronics

Background:

• Organic solar cells (OSCs) offer advantages for next-generation photovoltaics but are limited by voltage losses.
• Achieving high luminescence and charge transport in nonfullerene acceptors (NFAs) is challenging due to complex structure-packing relationships.

Purpose of the Study:

• To demonstrate a molecular design concept for precise control over intermolecular packing in A-DA'D-A-type NFAs.
• To overcome efficiency bottlenecks in OSCs by optimizing NFA solid-state packing.

Main Methods:

• Systematic substituent modification (methoxy, methyl, hydrogen, fluorine) on the remote phenyl ring of NFAs.
• Investigated the impact of substituents on photoluminescence quantum yield (PLQY), charge transport, and intermolecular stacking (end-bridge/E-B and end-end/E-E).

Main Results:

• Methoxy-substituted AQxPO enhanced PLQY (9.96%) by reducing E-B stacking but hindered charge transport.
• Fluorine-substituted AQxPF promoted E-B/E-E stacking, improving carrier transport but lowering PLQY (4.78%).
• Hydrogen-substituted AQxPH balanced E-B suppression and E-E interactions, yielding high PLQY and superior charge transport.

Conclusions:

• The D18:AQxPH-based OSC achieved a 20.9% PCE with a high open-circuit voltage (V_OC) of 0.925 V.
• Achieved ultralow non-radiative energy loss (0.176 eV) through optimized molecular packing.
• This study provides a design principle for enhancing OSC efficiency via precise stacking control.