Fluorinated Perylene Diimide Dimer for Organic Solar Cells as Non-fullerene Acceptor

Abstract

Fluorination has been widely applied in modification of photovoltaic materials, especially fused ring electron acceptors and polymer donors, but rarely in perylene diimides (PDIs)-based acceptors. The di-PDI-2F is facilely obtained by a one-step synthesis via stannylation/Stille cross-coupling reaction. Furtherly, we conducted a comparison study between the newly designed fluorinated PDI dimer di-PDI-2F and its non-fluorinated analogue di-PDI. After fluorination, the energy levels are downshifted, and the absorption spectrum is greatly blue shifted. When paired with a medium band-gap donor PM6, di-PDI-2F based organic solar cells show reduced trap-assisted and bimolecular recombination as well as better exciton dissociation and charge collection efficiency than that of di-PDI based ones, thus a greatly enhanced fill factor (FF), together with improved open circuit voltage (Voc) and short circuit current density (Jsc), leading to a superior power conversion efficiency. This fact suggests the potential of fluorination strategy on PDI based acceptors.