Controlled n-Doping of Naphthalene-Diimide-Based 2D Polymers

Area of Science:

• Materials Science
• Organic Electronics
• Semiconductor Physics

Background:

• Two-dimensional polymers (2DPs) are promising organic semiconductors but suffer from low conductivity due to limited charge carriers.
• Naphthalene diimide (NDI)-based 2DPs are structurally well-defined and porous but typically exhibit insulating properties.

Purpose of the Study:

• To enhance the bulk conductivity of NDI-containing 2DP semiconductors.
• To investigate the effects of controlled n-doping on the electronic properties of 2DPs.
• To explore the potential of doped 2DPs for electronic and spintronic applications.

Main Methods:

• Controlled n-doping of NDI-containing 2DPs using cobaltocene (CoCp2).
• Characterization using optical spectroscopy, transient microwave spectroscopy, and electron-spin resonance (ESR) spectroscopy.
• Density functional theory (DFT) calculations to understand electronic coupling and transport pathways.

Main Results:

• As-prepared NDI-based 2DPs are semiconductors with sub-2 eV optical bandgaps and charge-carrier lifetimes in the nanosecond range.
• Doping with CoCp2 yields NDI-radical anions, significantly increasing bulk conductivity to over 10^-4 S cm^-1.
• DFT calculations indicate that out-of-plane (π-stacking) directions are crucial for electronic transport.

Conclusions:

• Controlled molecular doping is an effective strategy to enhance the conductivity of 2DPs.
• Doped NDI-based 2DPs are paramagnetic n-type semiconductors with measurable bulk conductivity.
• These materials show promise for applications in electronic and spintronic devices.