Engineering the Doping Efficiency in Pentacene Thin Films for High Thermoelectric Performance.

Area of Science:

• Materials Science
• Organic Electronics
• Thermoelectrics

Background:

• Pentacene (PEN) shows promise for organic thermoelectric (TE) materials due to high mobility and Seebeck coefficient.
• Low intrinsic conductivity of PEN hinders its application in thermoelectric devices.

Purpose of the Study:

• To enhance the conductivity of pentacene thin films for improved thermoelectric performance.
• To investigate the effectiveness of interface doping using hexacyano-trimethylene-cyclopropane (CN6-CP) as a dopant.

Main Methods:

• Fabrication of bilayer-structured thin films using PEN and CN6-CP.
• Characterization using time-of-flight secondary ion mass spectrometry, UV-vis spectroscopy, electron spin-resonance, ultraviolet photoelectron spectroscopy, and X-ray photoelectron spectroscopy.
• Measurement of electrical conductivity and thermoelectric properties.

Main Results:

• Achieved high conductivity in interface-doped PEN films with almost intact crystallinity and efficient charge carrier generation.
• Demonstrated integral charge transfer between PEN and CN6-CP molecules.
• Reached a maximum conductivity of 10.1 S cm^-1 for PEN films on SiO₂/Si substrates, the highest reported for doped PEN thin films.
• Optimized thermoelectric performance with a power factor of 36.4 μW m^-1 K^-2.

Conclusions:

• Interface doping with a strong electron acceptor like CN6-CP is a viable strategy to enhance the conductivity of PEN.
• This approach significantly improves the thermoelectric performance of small molecular organic semiconductors.
• The developed method offers a promising route for advancing organic thermoelectric materials.