Experimentally Calibrated Kinetic Monte Carlo Model Reproduces Organic Solar Cell Current-Voltage Curve

TL;DR

This study presents an experimentally calibrated Kinetic Monte Carlo model that accurately reproduces the current-voltage characteristics of organic solar cells by integrating experimental data on device properties.

Contribution

The paper introduces a KMC model calibrated with experimental measurements to predict organic solar cell J-V curves, addressing previous simulation challenges.

Findings

The calibrated model accurately reproduces experimental J-V curves.

Experimental calibration of injection barriers and morphology is crucial.

Microscopic KMC results are relevant for real devices.

Abstract

Kinetic Monte Carlo (KMC) simulations are a powerful tool to study the dynamics of charge carriers in organic photovoltaics. However, the key characteristic of any photovoltaic device, its current-voltage ($J$-$V$) curve under solar illumination, has proven challenging to simulate using KMC. The main challenges arise from the presence of injecting contacts and the importance of charge recombination when the internal electric field is low, i.e., close to open-circuit conditions. In this work, an experimentally calibrated KMC model is presented that can fully predict the $J$-$V$ curve of a disordered organic solar cell. It is shown that it is crucial to make experimentally justified assumptions on the injection barriers, the blend morphology, and the kinetics of the charge transfer state involved in geminate and nongeminate recombination. All of these properties are independently calibrated using charge extraction, electron microscopy, and transient absorption measurements, respectively. Clear evidence is provided that the conclusions drawn from microscopic and transient KMC modeling are indeed relevant for real operating organic solar cell devices.