Polar-Twisted Electron-Transport Layer Simultaneously Breaks Efficiency-Flexibility-Cost Limits in Organic Solar...

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Perylene diimide (PDI)-based electron-transport layers (ETLs) are crucial for organic solar cell (OSC) performance, influencing charge extraction, recombination, and operational stability.
• Current molecular design strategies for PDIs lack universally applicable principles, hindering further advancements in OSC technology.

Purpose of the Study:

• To establish a transferable molecular design framework for PDI-ETLs by combining bay-position engineering with polar, bulky side-chain modulation.
• To enhance additive-free alcohol solubility, prevent over-crystallization, and reduce oxidative degradation of PDI-based ETLs.

Main Methods:

• Development of a PDI-ETL molecular design framework incorporating bay-position engineering and side-chain modification.
• Synthesis and characterization of the novel H75-DMA PDI-ETL material.
• Fabrication and testing of binary organic solar cells (OSCs) utilizing the H75-DMA ETL.

Main Results:

• The H75-DMA ETL effectively suppresses reactive-oxygen-driven degradation and interfacial trap accumulation, stabilizing energetics and electron transport.
• Organic solar cells (OSCs) incorporating H75-DMA achieved power conversion efficiencies (PCE) exceeding 20%.
• Flexible devices demonstrated enhanced mechanical toughness and bending durability, with improved light utilization in semitransparent devices due to a smooth cathode interface.

Conclusions:

• The proposed PDI-ETL molecular design framework offers a pathway to improved OSC performance, stability, and durability.
• H75-DMA enables the use of cost-effective copper cathodes with minimal loss in power conversion efficiency compared to silver.
• This advancement contributes to the development of more efficient, robust, and economically viable organic solar cells.