Alkenyl Carboxylic Acid: Engineering the Nanomorphology in Polymer-Polymer Solar Cells as Solvent Additive

Area of Science:

• Materials Science
• Organic Electronics
• Renewable Energy

Background:

• Polymer-polymer non-fullerene solar cells offer a promising alternative for renewable energy generation.
• Processing additives are crucial for controlling morphology and enhancing the performance of these devices.
• Current additives, like DIO, often contain halogens, raising environmental concerns.

Purpose of the Study:

• To investigate the efficacy of halogen-free alkenyl carboxylic acids as solvent additives in polymer-polymer non-fullerene solar cells.
• To understand the impact of these additives on film absorption, morphology, carrier generation, transport, and recombination.
• To identify optimal additive structures for improved device performance and sustainability.

Main Methods:

• Systematic investigation of trans-2-hexenoic acid (CA-6), trans-2-decenoic acid (CA-10), and 9-tetradecenoic acid (CA-14) as solvent additives.
• Analysis of film absorption, morphology, carrier generation, transport, and recombination in all-polymer solar cells.
• Comparison of device performance with and without additives, and against a standard additive (DIO).

Main Results:

• Alkenyl carboxylic acids significantly influence polymer acceptor aggregation, leading to improved phase segregation and nanomorphology.
• Trans-2-decenoic acid (CA-10) demonstrated optimal performance due to fine phase separation, balanced charge transport, and suppressed recombination.
• Devices treated with CA-10 achieved a power conversion efficiency (PCE) of 5.71%, a substantial increase from the as-cast device (3.71%) and slightly exceeding DIO-treated devices (5.68%).

Conclusions:

• Halogen-free alkenyl carboxylic acids are effective and sustainable processing additives for polymer-polymer non-fullerene solar cells.
• CA-10 shows particular promise for enhancing device performance through controlled nanomorphology.
• These findings pave the way for more environmentally friendly and efficient organic solar cell technologies.