Exploiting Bis-Sulfonimide Featuring Multiple d-pπ Bonds to Construct Interlayers for Organic Solar Cells

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Organic solar cells (OSCs) require efficient cathode interlayer materials (CIMs) to optimize charge extraction and device stability.
• Traditional CIMs often face limitations in processability, energy level alignment, and long-term operational stability.
• Developing novel building blocks for CIMs is crucial for advancing OSC performance.

Purpose of the Study:

• To introduce bis-sulfonimide (BSI) as a novel, general, and extendable building block for multifunctional CIMs in OSCs.
• To synthesize and characterize BSI-based CIMs, evaluating their properties for improved OSC performance.
• To demonstrate the potential of BSI-based CIMs for achieving high efficiency and operational stability in OSCs.

Main Methods:

• Synthesis of a series of multifunctional CIMs utilizing the BSI building block.
• Characterization of CIM properties, including alcohol processability, work function, energy levels, conductivity, and crystallinity.
• Fabrication and testing of OSC devices incorporating the developed BSI-based CIMs with different active layers.
• Performance evaluation under continuous illumination and assessment of thickness-insensitivity.

Main Results:

• An illustrative CIM, BSIz-TT-PDI, exhibited high conductivity (>5×10⁻³ S/cm), tunable work function, and optimized energy levels.
• BSIz-TT-PDI-based OSCs achieved a power conversion efficiency of 18.08% with a PM6:Y6 active layer.
• Devices demonstrated excellent operational stability, retaining 84% performance after 1100 hours of continuous illumination.
• The CIM showed remarkable thickness insensitivity (5-90 nm) and compatibility with various active layers, leading to a record efficiency of 19.80% with a PM6:BTP-eC9:L8-BO active layer.

Conclusions:

• Bis-sulfonimide (BSI) is a highly effective building block for developing advanced CIMs for OSCs.
• BSI-based CIMs enable precise interfacial engineering, leading to significant improvements in OSC efficiency and stability.
• This work pioneers thickness-insensitive CIMs, offering a pathway towards robust and high-performance organic solar cells.