Zwitterionic Bioinspired Acceptor-Acceptor (A₁-A₂) Type Interlayers for Organic Solar Cells

Area of Science:

• Materials Science
• Organic Electronics
• Photovoltaics

Background:

• Interlayer materials are critical for organic solar cell (OSC) performance, requiring precise electronic matching with active layers and thickness tolerance.
• Zwitterionic polymers are promising interlayer candidates, but exploration beyond sulfobetaine (SB) and understanding anionic group contributions are limited.

Purpose of the Study:

• To explore novel zwitterionic interlayer materials beyond sulfobetaine (SB) for organic solar cells (OSCs).
• To investigate the impact of synergistic side chain and backbone engineering on interlayer properties and device performance.
• To demonstrate a new bioinspired zwitterionic material for high-efficiency and stable organic photovoltaics.

Main Methods:

• Engineered a bioinspired zwitterionic polymer (PDITz-PC) with fluorinated phosphatidylcholine-based side chains and an acceptor-acceptor (A1-A2) conjugated backbone.
• Characterized the material's electronic properties, molecular packing, and interfacial characteristics.
• Fabricated and tested organic solar cells (OSCs) with the PDITz-PC interlayer across various active layer systems and device areas.

Main Results:

• PDITz-PC achieved deep frontier molecular orbital energy levels, suppressed parasitic absorption, and reduced hydrophilicity.
• The interlayer demonstrated strong work function modification, superior electrical properties, and excellent interfacial contact.
• Organic solar cells (OSCs) with PDITz-PC exhibited high power conversion efficiencies (PCEs) for small and large areas, improved operational stability, and good thickness tolerance (92% PCE retention at 115 nm).

Conclusions:

• Synchronized side chain and backbone engineering is crucial for developing advanced interlayer materials in organic photovoltaics (OPVs).
• PDITz-PC offers a strategic route to high-performance, durable, and scalable organic solar cells (OSCs) by enhancing exciton dissociation, charge transport, and reducing recombination.
• This work highlights the potential of bioinspired zwitterionic materials for next-generation organic electronics.