Fine Optimization of Morphology Evolution Kinetics with Binary Additives for Efficient Non-Fullerene Organic Solar...

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• The power conversion efficiency (PCE) of polymer solar cells (PSCs) is critically dependent on the morphology of the active layer.
• Optimizing the bulk heterojunction (BHJ) morphology is essential for enhancing charge generation and transport in PSCs.

Purpose of the Study:

• To investigate the impact of binary solvent additives, octance-1,8-dithiol (ODT) and 1,8-diiodooctane (DIO), on the BHJ morphology of FTAZ:ITIC-Th based PSCs.
• To elucidate the distinct roles of ODT and DIO in controlling the film-forming process and molecular packing.

Main Methods:

• Fabrication of PSCs using FTAZ:ITIC-Th active layers with varying ratios of ODT and DIO as solvent additives.
• Morphological characterization techniques to analyze blend film structure.
• In situ grazing incidence wide-angle X-ray scattering (GIWAXS) to monitor film formation dynamics.

Main Results:

• PSCs treated with ODT and DIO achieved approximately 11% efficiency, a 10% relative increase compared to untreated devices.
• Morphological characterizations demonstrated that binary solvent additives effectively manipulate molecular packing and phase separation.
• In situ GIWAXS revealed that ODT influences initial film formation, while DIO plays a role in later stages, establishing the final photoactive film.

Conclusions:

• The strategic use of ODT and DIO as binary solvent additives enables precise control over active layer morphology in PSCs.
• An optimal ratio of ODT:DIO (0.375%:0.125%) was identified, leading to optimized BHJ morphology and enhanced device performance.
• Understanding the distinct temporal roles of solvent additives is crucial for designing high-efficiency PSCs.