Monte Carlo Simulation of Carrier Diffusion in Organic Thin Films with Morphological Inhomogeneity

TL;DR

This study uses Monte Carlo simulations to explore how morphological inhomogeneity affects carrier diffusion in organic thin films, revealing complex behaviors influenced by morphology and energetic disorder.

Contribution

It introduces a simulation approach that accounts for morphological inhomogeneity and its impact on charge carrier diffusion in organic thin films.

Findings

Carrier diffusion decreases with disorder in homogeneous films.

In inhomogeneous films, diffusion initially increases with decreasing disorder, then decreases after an optimum.

Morphology-dependent carrier spreading significantly influences charge transport.

Abstract

Monte Carlo simulation was carried out to understand the influence of morphological inhomogeneity on carrier diffusion in organic thin films. The morphological inhomogeneity was considered in the simulation by incorporating the regions of low energetic disorder in a host lattice of high energetic disorder which decreases the overall energetic disorder of the system. For the homogeneous films, the carrier diffusion was found to decrease upon decreasing the energetic disorder. In contrast to this, in the case of inhomogeneous films the carrier diffusion enhanced upon decreasing the overall energetic disorder, up to an optimum value and beyond which the carrier diffusion decreased. Through our simulation, we observed that the behavior of carrier diffusion in the inhomogeneous case is due to the morphology dependent carrier spreading, which acts in addition to the thermal and non-thermal field assisted diffusion mechanisms. This morphological dependence of carrier spreading arises due to the generation of packets of carriers with different jump rates, which is after effect of slow relaxation of the carriers generated in the less disordered regions of inhomogeneous system. Our simulation of morphology dependent carrier spreading and its influence on the basic diffusion process provide deeper insight into the charge transport mechanisms in organic thin films.