Phosphate Ester-Modified Acceptor Additives Enable Concurrent Vertical Morphology and Interfacial Engineering for...

Area of Science:

• Materials Science
• Organic Electronics
• Renewable Energy

Background:

• Organic solar cells (OSCs) utilizing non-fullerene acceptors (NFAs) show rapid progress.
• Further advancements are limited by challenges in vertical morphology control and energy alignment at the acceptor-cathode interface.

Purpose of the Study:

• To develop a molecular engineering strategy to address vertical morphology and interfacial energy alignment issues in OSCs.
• To improve the power conversion efficiency (PCE) and operational stability of NFA-based OSCs.

Main Methods:

• Synthesized two NFA derivatives (1POE and 2POE) with polar phosphate ester groups.
• Utilized these derivatives as non-volatile solid additives during layer-by-layer processing.
• Analyzed the resulting vertical composition redistribution and interfacial energetics.

Main Results:

• The additives induced vertical composition redistribution, forming a graded donor-acceptor-additive architecture.
• This resulted in strengthened intermolecular interactions, raised surface energy, and improved electron extraction.
• Devices with 1POE and 2POE achieved PCEs of 19.87% and 19.28%, respectively, outperforming controls (18.83%).
• A PCE of 20.90% was achieved in a ternary system, demonstrating universality.

Conclusions:

• Phosphate ester-based additive design enables concurrent optimization of vertical phase distribution and interfacial energetics.
• This provides a practical approach for developing high-efficiency and stable OSCs.