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

• Published in: Journal of physical chemistry. C Vol. 117; no. 47; pp. 24663 - 24672
• Main Authors: Mohan, S. Raj, Singh, Manoranjan P, Joshi, M. P, Kukreja, L. M
• Format: Journal Article
• Language: English
• Published: Columbus, OH American Chemical Society 27.11.2013
• Subjects: Condensed matter: structure, mechanical and thermal properties; Diffusion in solids; Exact sciences and technology; Physics; Transport properties of condensed matter (nonelectronic); Disordered systems; Digital simulation; Charge transport; Thin films; Relaxation; Monte Carlo methods; Morphology; Charge carrier generation; Diffusion process; Inhomogeneity; Transport processes; Diffusion; Microstructure; Carrier mobility
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp4006839

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, 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 nonthermal 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 the after effect of slow relaxation of the carriers generated in the less disordered regions of the inhomogeneous system. Our simulation of morphology-dependent carrier spreading and its influence on the basic diffusion process provides deeper insight into the charge transport mechanisms in organic thin films.