Raising Dielectric Permittivity Mitigates Dopant-Induced Disorder in Conjugated Polymers

Area of Science:

• Materials Science
• Condensed Matter Physics
• Polymer Electronics

Background:

• Conjugated polymers require doping to achieve sufficient electrical conductivity for electronic and energy applications.
• Doping introduces Coulomb interactions between dopants and carriers, leading to poor screening, broadened electronic density-of-states (DOS), and negative impacts on charge transport properties.

Purpose of the Study:

• To investigate the effects of dopant-induced disorder on the Seebeck coefficient and electrical conductivity of semiconducting polymers.
• To demonstrate a method for mitigating the negative impacts of dopant-induced disorder on charge transport.

Main Methods:

• Utilized simulations based on a modified Gaussian disorder model with Miller-Abrahams hopping rates.
• Investigated the influence of varying dielectric permittivity on charge transport properties.
• Experimentally validated findings using iodine-doped P3HT and P3HT blended with barium titanate (BaTiO3) nanoparticles.

Main Results:

• Dopant-induced broadening of the DOS negatively affects the Seebeck coefficient versus electrical conductivity trade-off.
• Increasing the polymer's dielectric permittivity effectively mitigates dopant-carrier Coulomb interactions.
• Simultaneous improvements in conductivity and Seebeck coefficient were observed.
• Experimental addition of BaTiO3 nanoparticles resulted in a fourfold increase in power factor.

Conclusions:

• Enhancing dielectric permittivity is a viable strategy to reduce dopant-carrier Coulomb interactions in conjugated polymers.
• This approach offers a promising pathway to mitigate adverse effects on charge transport and improve material performance for electronic and energy applications.