Fast and Accurate Simulations of Partially Delocalised Charge Separation in Organic Semiconductors

TL;DR

This paper introduces an extended, computationally efficient kinetic Monte Carlo model called jKMC for simulating charge separation in organic semiconductors, capturing delocalisation effects and improving predictive capabilities.

Contribution

The paper extends the jKMC model to describe charge-transfer state separation, enabling accurate, low-cost simulations of delocalised charge transport in OPVs.

Findings

jKMC reproduces charge-separation efficiencies seen in more complex models.

The extended jKMC is computationally cheaper than dKMC.

jKMC can be integrated into existing KMC frameworks.

Abstract

Accurate computational screening of candidate materials promises to accelerate the discovery of higher-efficiency organic photovoltaics (OPVs). However, modelling charge separation in OPVs is challenging because accurate models must include disorder, polaron formation, and charge delocalisation. Delocalised kinetic Monte Carlo (dKMC) includes these three essential ingredients, but it suffers from high computational cost. Recently, we developed jumping kinetic Monte Carlo (jKMC), a computationally cheap and accurate model of delocalised charge transport that models transport over a lattice of identical, spherical polarons. Here, we extend jKMC to describe the separation of a charge-transfer state, showing that this simplified approach can reproduce the considerable improvements in charge-separation efficiencies caused by delocalisation and first seen in dKMC. The low computational cost and simplicity of jKMC allows it to be applied to parameter regimes intractable by dKMC, and ensures jKMC can be easily incorporated into any existing KMC model.