Developing a Fluorinated Benzothiadiazole-Based Polymer Donor as Guest to Construct High-Performance Ternary Solar...

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Benzothiadiazole (BT) is promising for solar cells, but BT-based polymer donors show limited efficiency in fused-ring small molecular acceptor-based polymer solar cells (PSCs).
• Developing high-performance polymer donors is crucial for advancing PSC technology.

Purpose of the Study:

• To design and synthesize a novel D-A polymer donor (F-1) incorporating a fluorinated BT (ffBT) acceptor unit and a chlorinated benzo[1,2-b:4,5-b']dithiophene (BDT-2Cl) donor unit.
• To investigate the impact of F-1 on the morphology, energy levels, and performance of PSCs, particularly in ternary device configurations.

Main Methods:

• Synthesis of the D-A polymer donor F-1.
• Fabrication of ternary polymer solar cells using F-1, PM6, and L8-BO.
• Characterization of film morphology, energy levels, and photovoltaic performance.

Main Results:

• The ffBT unit in F-1 lowered energy levels, enhancing open-circuit voltage, and facilitated noncovalent S···F interactions, improving molecular planarity and crystallinity.
• Incorporating F-1 into PM6:L8-BO blends resulted in improved film morphology, phase separation, and molecular arrangement.
• The ternary device with 5% F-1 achieved a power conversion efficiency (PCE) of 19.47%, outperforming the binary device (18.35%).

Conclusions:

• The study demonstrates a viable strategy for developing high-performance polymer donors using noncovalent conformational locks within BT-based systems.
• Constructing ternary solar cells offers an effective approach to further enhance the performance of polymer solar cells.