First-principles modeling of charge transport in amorphous semiconducting polymer

Understanding charge transport in amorphous organic materials is crucial for improving organic electronic devices such as OLEDs and solar cells. While charge transport in disordered organic semiconductors has been treated phenomenologically, we employ first-principles calculations to determine the morphology of disordered systems. A tight-binding model coupled to the dielectric medium provides energetics. Charge transport is described by thermally activated hopping, with rates given by Marcus theory, which depends on electronic coupling and activation barriers. Building on our previous work using the tight-binding model to describe exciton energetics and structure, we now apply it to calculate electronic coupling and activation barriers for charge hopping in a disordered polymer. We introduce a dielectric-stabilized transition state delocalized over two chains (i.e., the initial and final state). We use polymer chain configurations from well-equilibrated atomistic simulation to explore heterogeneity in charge hopping rates and timescales. Using the network of accessible hops along and between chains, we predict charge mobility for amorphous poly(3-hexylthiophene) [P3HT] melt, resulting in good agreement with mobility experiments without adjusting any parameters. This approach provides insight into charge transport mechanisms in amorphous organic semiconductors, potentially guiding the design of more efficient organic electronic devices.