Supramolecular Seeding-Induced Fibrillar Refinement for High Efficiency and Stable Organic Solar Cells

Area of Science:

• Materials Science
• Organic Electronics
• Supramolecular Chemistry

Background:

• Organic solar cells (OSCs) face challenges in morphology control and long-term stability due to uncoordinated donor-acceptor crystallization during solution processing.
• Optimizing morphology is crucial for efficient exciton harvesting, charge generation, and balanced charge transport in OSCs.

Purpose of the Study:

• To develop a supramolecular crystallization seeding strategy to enhance morphology and stability in organic solar cells.
• To engineer a thermodynamic compatibility gradient to control the crystallization sequence of donor and acceptor materials.

Main Methods:

• Introduction of a hydroxyl-terminated, crystalline acceptor (Y-OH) into the D18/L8-BO system.
• Engineering a hierarchical thermodynamic compatibility gradient (χD18/Y-OH > χL8-BO/Y-OH > χD18/L8-BO).
• In situ UV-vis measurements to monitor early-stage ordering and morphology evolution.

Main Results:

• Y-OH demonstrated interfacial activity and an interfacial distribution tendency, participating in initial morphology evolution.
• Steered L8-BO organization into a refined interpenetrating fibrillar network with reduced fibril diameters.
• Optimized ternary devices achieved a power conversion efficiency (PCE) of 20.90%, with enhanced short-circuit current density (JSC) and fill factor (FF).
• Devices retained ≈83% of initial efficiency after 900 hours at 65 °C due to supramolecular interactions preventing morphology relaxation.

Conclusions:

• Supramolecular crystallization seeding is an effective strategy for simultaneously improving efficiency and thermal stability in OSCs.
• Hierarchical thermodynamic compatibility engineering enables precise control over multicomponent film morphology.
• Hydroxyl-enabled supramolecular interactions provide noncovalent anchoring, crucial for retarding morphology relaxation and enhancing device longevity.