Intermolecular Energy and Electron Transfer by Non-orthogonal Configuration Interaction

Intermolecular electron and energy transfer plays a fundamental role in organic solar cells, which have practical advantages over silicon-based cells but still have to catch up in efficiency.

This project focuses on the understanding of the formation of charge carriers through Multiple Exciton Generation. It aims to clarify the mechanism of the separation of the double triplet state formed by singlet fission and explores the possibility to enhance the electron-hole separation by Intermolecular Coulombic Decay.

Our Non-Orthogonal Configuration Interaction based on Fragments (NOCI-F) offers a reliable way to evaluate the electronic coupling between diabatic states of an ensemble of molecules involved in these processes. The molecular electronic states are each characterized by correlated wave functions and the antisymmetrized spin-adapted products thereof form the many- electron basis sets for our NOCI-F expansion.

NOCI-F is implemented in the massively parallel and GPU-accelerated open source code GronOR to overcome the computational complications inherent to the use of non-orthogonal many-electron basis sets.

Our computational study is intended to result in design rules for materials with improved energy and charge transfer properties, eventually leading to more efficient organic solar cells.