How Does Polymorphism Affect the Interfacial Charge-Transfer States in Organic Photovoltaics?

Abstract

The bulk heterojunction in organic photovoltaic (OPV) devices is a mixture of polymer (electron donor) and an electron acceptor material (typically functionalized fullerenes), and it is crucial for the device operation, as this is where excitons are split into electrons and holes to produce current. Nonfullerene acceptors (NFAs) are promising new materials for improving the device efficiency, and their solid-state arrangement with respect to the electron donor polymer is critical for the charge mobility and the performance of OPV devices. Although there have been numerous studies on NFAs, most of the current understanding comes from empirical considerations, with little atomistic-level interpretation of why and how the packing influences the charge-transport properties of these materials. In this work, we describe large-scale (with up to 3462 atoms) density functional theory simulations for ground and excited states on a number of polymer–NFA interfaces of realistic size, whose NFA domains consist of poly...