Multi-Fluorination of Quinoxaline-Fused-Core-Based Non-Fullerene Acceptors with Modulated Molecular Stacking for...

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Quinoxaline (Qx)-fused-core small molecular acceptors (SMAs) are promising for organic solar cells (OSCs) due to low energy loss.
• However, challenges like excessive molecular stacking and poor processability hinder their practical application and stability.

Purpose of the Study:

• To synthesize novel SMAs by incorporating multiple fluorine atoms into the Qx2 core to improve performance and processability.
• To investigate the impact of fluorine substitution on molecular interactions, energy levels, and stacking modes in OSCs.

Main Methods:

• Synthesis of two novel SMAs, Qx2-D7F and Qx2-D10F, featuring multiple fluorine atoms.
• Theoretical calculations and experimental characterization of material properties and device performance.
• Fabrication and testing of organic solar cell devices using the synthesized SMAs.

Main Results:

• Fluorine incorporation tuned energy levels and stacking modes by altering local dipole moments and electrostatic potentials.
• D18:Qx2-D7F blends showed optimal phase separation and balanced charge mobility, leading to a high power conversion efficiency (PCE) of 18.12% in OSCs.
• Ternary devices achieved 20.25% PCE, and large-area slot-die-coated devices reached 14.61% PCE, demonstrating enhanced processability and scalability.
• Devices exhibited excellent thermal and photostability with T80 lifetimes exceeding 3500 and 2000 hours, respectively.

Conclusions:

• Multi-fluorination is an effective strategy to precisely regulate donor-acceptor interactions, enhancing morphology and stability in OSCs.
• The developed Qx2-based SMAs offer improved processability, efficiency, and operational stability for next-generation organic solar cells.