A graph based approach to model charge transport in semiconducting polymers

Ramin Noruzi,Balaji Sesha Sarath Pokuri,Baskar Ganapathysubramanian,Michael L Chabinyc,Eunhee Lim

doi:10.1038/s41524-022-00714-w

Ramin Noruzi, Balaji Sesha Sarath Pokuri + Show 3 more

Open Access

https://doi.org/10.1038/s41524-022-00714-w

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Abstract

Charge transport in molecular solids, such as semiconducting polymers, is strongly affected by packing and structural order over several length scales. Conventional approaches to modeling these phenomena range from analytical models to numerical models using quantum mechanical calculations. While analytical approaches cannot account for detailed structural effects, numerical models are expensive for exhaustive (and statistically significant) analysis. Here, we report a computationally scalable methodology using graph theory to explore the influence of molecular ordering on charge mobility. This model accurately reproduces the analytical results for transport in nematic and isotropic systems, as well as experimental results of the dependence of the charge carrier mobility on orientation correlation length for polymers. We further model how defect distribution (correlated and uncorrelated) in semiconducting polymers can modify the mobility, predicting a critical defect density above which the mobility plummets. This work enables rapid (and computationally extensible) evaluation of charge mobility semiconducting polymer devices.

Highlights

Predicting the charge carrier mobility of semicrystalline polymers is challenging because of the interplay between ordered and disordered regions[1,2]
The effect of polymer chain length and increases the polymer chains will become disordered if they molecular orientation on charge mobility was modeled analytically by Pearson and Pincus[25] and recently re-investigated using a similar approach[45]
One experimental metric for the length scale of alignment of polymer backbones is the orientafor a charge to diffuse along the extent of a polymer chain and tional correlation length (OCL), which is defined as the average one value of the time to hop between chains

Summary

Introduction

Predicting the charge carrier mobility of semicrystalline polymers is challenging because of the interplay between ordered and disordered regions[1,2]. Polymer chains in ordered regions are extended with long conjugation lengths and packed such that the interchain electronic coupling is weak, but still significant for charge transport. Transport may occur through extended electronic states whereas in the disordered regions charges are thought to move by hopping between localized sites[3,4]. The ability of high resolution transmission electron microscopy (HR-TEM)[5–11] and X-ray scattering methods[12–14] to reveal the detailed morphology of semiconducting polymers presents an opportunity to reveal how ordered and disordered regions impact charge transport. The challenge is to model how charge transport occurs between these two regions, which can guide the design of new polymers and processing routes to achieve higher carrier mobilities

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