Naphthalene-Diimide-Based Ionenes as Universal Interlayers for Efficient Organic Solar Cells

Area of Science:

• Materials Science
• Organic Electronics
• Polymer Chemistry

Background:

• Organic solar cells (OSCs) require efficient charge transport and interfacial engineering for optimal performance.
• Developing universal interlayers that enhance electron injection and extraction is crucial for advancing OSC technology.

Purpose of the Study:

• To synthesize novel self-doping ionene polymers based on naphthalene diimide (NDI).
• To investigate the efficacy of these polymers as universal interlayers in various organic solar cell architectures.
• To correlate polymer properties with device performance and understand interfacial effects.

Main Methods:

• Quaternization polymerization of functional naphthalene diimide (NDI) with dibromopropane (NDI-NI) or dibromobutene (NDI-CI).
• Fabrication and characterization of fullerene-based, non-fullerene-based, and ternary OSCs utilizing the synthesized polymers as interlayers.
• Measurement of interfacial dipole, conductivity, electron mobility, work function, and device efficiency.

Main Results:

• Efficient synthesis of NDI-based ionene polymers (NDI-NI and NDI-CI) as self-doping interlayers.
• Demonstrated universal applicability across different OSC types, achieving a maximum power conversion efficiency of 16.9%.
• NDI-NI exhibited superior interfacial dipole, conductivity, and electron mobility compared to NDI-CI, leading to higher device efficiencies.
• Effective reduction of metal work function and optimization of electrode-semiconductor contact.

Conclusions:

• Self-doping ionene polymers serve as effective universal interlayers for enhancing OSC performance.
• The synthesized NDI-based polymers successfully mitigate energy barriers in electron injection/extraction processes.
• Tailoring polymer properties, such as interfacial dipole and conductivity, is key to achieving high-efficiency organic electronics.