Efficient charge separation in organic photovoltaics through incoherent hopping

TL;DR

This paper shows that efficient charge separation in organic solar cells can be explained by an incoherent hopping mechanism, emphasizing the importance of bipolar transport and increased dimensionality for high efficiency.

Contribution

It introduces a kinetic Monte Carlo model incorporating on-chain delocalization to explain nearly field-independent charge separation in organic photovoltaics.

Findings

Charge separation efficiency is nearly field-independent.

Bipolar transport and higher dimensionality are crucial for efficiency.

The model aligns with experimental observations of molecular systems.

Abstract

We demonstrate that efficient and nearly field-independent charge separation in organic planar heterojunction solar cells can be described by an incoherent hopping mechanism. We model the separation efficiency of electron-hole pairs created at donor-acceptor organic interfaces. By using kinetic Monte Carlo simulations that include the effect of on-chain delocalization we show that efficient charge extraction to the electrodes requires bipolar transport and increased dimensionality. This model explains experimental results of almost field independent charge separation in some molecular systems and provides important guidelines at the molecular level for maximizing the efficiencies of organic solar cells.