Charge Conductivity in Donor-Acceptor Polymer Dispersions Measured with Time-Resolved Terahertz Spectroscopy

Area of Science:

• Materials Science
• Spectroscopy
• Organic Electronics

Background:

• Conjugated donor-acceptor co-polymers are crucial for organic electronics.
• Understanding their photoconductive properties is key to device optimization.
• Non-contact methods are desirable for probing material characteristics.

Purpose of the Study:

• To investigate the photoconductive properties of five distinct donor-acceptor co-polymers.
• To correlate polymer structure with charge transfer dynamics using ultrafast spectroscopy.
• To analyze conductivity kinetics and carrier properties under varying photoexcitation energies.

Main Methods:

• Utilized Ultrafast Time-Domain and Time-Resolved Terahertz (TDS/TRTS) spectroscopy.
• Dispersed co-polymers in room temperature toluene, a nonpolar dielectric solvent.
• Performed ab initio calculations via Density Functional Theory (DFT) for molecular orbital analysis.

Main Results:

• Time-Resolved Terahertz Spectroscopy (TRTS) effectively probed localized relative conductivity non-contactly.
• Photoconductivity kinetics and real/imaginary conductivity levels were contrasted across different polymer structures.
• Higher energy photoexcitation increased real photoconductivity up to threefold, influencing charge transfer efficacy.

Conclusions:

• The study provides insights into the relationship between polymer structure and photoconductivity.
• TRTS is a valuable tool for characterizing charge dynamics in co-polymer systems.
• DFT calculations support the understanding of charge transfer mechanisms elucidated by THz spectroscopy.