Delocalised kinetic Monte Carlo for simulating delocalisation-enhanced charge and exciton transport in disordered materials

Abstract

Charge transport is well understood in both highly ordered materials (band conduction) or highly disordered ones (hopping conduction). In moderately disordered materials -- including many organic semiconductors -- the approximations valid in either extreme break down, making it difficult to accurately model the conduction. In particular, describing wavefunction delocalisation requires a quantum treatment, which is difficult in disordered materials that lack periodicity. Here, we present the first three-dimensional model of partially delocalised charge and exciton transport in materials in the intermediate disorder regime. Our approach is based on polaron-transformed Redfield theory, but overcomes several computational roadblocks by mapping the quantum-mechanical techniques onto kinetic Monte Carlo. Our theory, delocalised kinetic Monte Carlo (dKMC), shows that the fundamental physics of transport in moderately disordered materials is that of charges hopping between partially delocalised electronic states. Our results reveal why standard kinetic Monte Carlo can dramatically underestimate mobilities even in disordered organic semiconductors, where even a little delocalisation can substantially enhance mobilities, as well as showing that three-dimensional calculations capture important delocalisation effects neglected in lower-dimensional approximations.

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Cited by in corpus (11)

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• Even a little delocalization produces large kinetic enhancements of charge-separation efficiency in organic photovoltaics
• Delocalisation enables efficient charge generation in organic photovoltaics, even with little to no energetic offset
• Mechanism of delocalisation-enhanced exciton transport in disordered organic semiconductors
• Holstein polaron transport from numerically "exact" real-time quantum dynamics simulations
• Jumping kinetic Monte Carlo: Fast and accurate simulations of partially delocalised charge transport in organic semiconductors
• Charge transport limited by nonlocal electron-phonon interaction. I. Hierarchical equations of motion approach
• Optimisation of ultrafast singlet fission in 1D rings towards unit efficiency
• Charging a quantum spin network towards Heisenberg-limited precision
• Partially polaron-transformed quantum master equation for exciton and charge transport dynamics
• Exciton transport in amorphous polymers and the role of morphology and thermalisation