# Effects of Disorder on Thermoelectric Properties of Semiconducting Polymers

## TL;DR

This study models how different types of disorder in semiconducting polymers influence their thermoelectric properties, revealing that positional disorder can enhance performance while energetic disorder hampers it.

## Contribution

It introduces a Gaussian disorder model combined with Pauli's master equation to analyze disorder effects on thermoelectric properties of polymers, providing new insights into optimizing TE performance.

## Key findings

- Positional disorder improves electrical conductivity and Seebeck coefficient.
- Energetic disorder hinders charge transport and reduces TE efficiency.
- Correlation in positional disorder affects conductivity, but energy correlation does not influence TE properties.

## Abstract

Organic materials have attracted recent interest as thermoelectric (TE) converters due to their low cost and ease of fabrication. We examine the effects of disorder on the TE properties of semiconducting polymers based on the Gaussian disorder model (GDM) for site energies while employing Pauli's master equation approach to model hopping between localized sites. Our model is in good agreement with experimental results and a useful tool to study hopping transport. We show that stronger overlap between sites can improve the electrical conductivity without adversely affecting the Seebeck coefficient. We find that positional disorder aids the formation of new conduction paths with an increased probability of carriers in high energy sites leading to a simultaneous increase in electrical conductivity and Seebeck coefficient. On the other hand, energetic disorder leads to increased energy gap between sites, hindering transport, and adversely affects both conductivity and Seebeck. Furthermore, positional correlation primarily affects conductivity, while correlation in energy has no effect on TE properties of polymers. Our results also show that the Lorenz number increases with Seebeck coefficient, largely deviating from the Sommerfeld value, in agreement with experiments and in contrast to band conductors. We conclude that reducing energetic disorder while increasing positional disorder can lead to higher TE power factors.