Conductive Ionenes Promote Interfacial Self-Doping for Efficient Organic Solar Cells

Area of Science:

• Materials Science
• Polymer Chemistry
• Organic Electronics

Background:

• Developing efficient interlayer materials is crucial for advancing organic solar cell (OSC) performance.
• Nonconjugated polymers often lack the inherent charge transfer capabilities needed for effective interfacial modification.

Purpose of the Study:

• To synthesize novel conductive ionenes by integrating electron donor and acceptor units.
• To investigate the self-doping mechanism and electronic properties of these nonconjugated polymers.
• To evaluate their performance as interlayer materials in various OSC architectures.

Main Methods:

• Synthesis of conductive ionenes via the Menshutkin reaction, combining dialkoxynaphthalene (DAN) and naphthalene diimide (NDI).
• Optimization of polymer film crystallinity and morphology by adjusting the DAN-to-NDI ratio.
• Characterization of charge transfer, electronic properties, and π-π interactions within the ionenes.
• Fabrication and testing of organic solar cells (fullerene-based, non-fullerene-based, and ternary) utilizing the synthesized ionenes as interlayers.

Main Results:

• Successful synthesis of conductive ionenes with strong intramolecular charge transfer from DAN to NDI.
• Demonstration of self-doping in nonconjugated polymers, attributed to enhanced π-π interactions.
• Significant improvement in OSC performance across different architectures, achieving a maximum power conversion efficiency of 17.05%.
• Effective interfacial modification and promotion of self-doping by the ionene interlayers over a thickness range of 8–40 nm.

Conclusions:

• This work presents the first instance of electron donor-induced doping in nonconjugated polymers.
• The developed conductive ionenes serve as efficient interlayer materials, boosting OSC performance through interfacial self-doping.
• This strategy opens new avenues for designing advanced materials for organic electronics and energy applications.