Influence of structural defects and oxidation onto hole conductivity in P3HT

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Chemistry

Background:

• Poly(3-hexylthiophene) is a promising organic semiconductor.
• Understanding charge transport is crucial for electronic applications.
• Structural defects and impurities can degrade material performance.

Purpose of the Study:

• To investigate the impact of structural imperfections and oxygen impurities on the quantum conductance of poly(3-hexylthiophene).
• To determine how molecular structure, stacking, and oxidation affect charge transport properties.

Main Methods:

• First-principles calculations.
• Solving the scattering problem for molecular structures.
• Density Functional Theory (DFT) for structural optimization.
• Wentzel-Kramers-Brillouin (WKB) approximation for conductivity analysis.

Main Results:

• Conductivity perpendicular to polymer chains is highly sensitive to stacking geometry.
• Local relaxation can restore conductance in bent or twisted chains, but sharp kinks (>60° rotation, <17 Å curvature) cause significant drops.
• Intrachain transmission is largely unaffected by isomer defects.
• Oxidation of side chains or sulfur has minimal effect, but oxidation of thiophene carbon atoms drastically reduces conductance.

Conclusions:

• Stacking geometry and severe structural defects are critical factors limiting poly(3-hexylthiophene) conductivity.
• Specific oxidation of the thiophene ring is detrimental to coherent transport.
• These findings provide insights for designing and processing organic semiconductors with improved performance.