Morphological Control of Donor/Acceptor Interfaces in All-Polymer Solar Cells Using a Pentafluorobenzene-Based Additive

We report a pentafluorobenzene-based additive (FPE) to control the donor/acceptor (D/A) interfacial morphology via quadrupolar electrostatic interactions between donor and acceptor polymers in all-polymer solar cells (allPSCs). The morphology changes are investigated using a combination of atomic force microscopy, grazing incidence wide-angle X-ray scattering, and near-edge X-ray absorption fine-structure spectroscopy. Unlike a conventional solvent additive, such as 1,8-diiodooctane, a bicontinuous interpenetrating morphology without large-scale phase separation and an enhanced pi-pi stacking with face-on orientation are found in the FPE processed blended films. These morphology changes improve the charge carrier extraction and charge transport between D/A interfaces to achieve an increase in the photovoltaic performance of all-PSCs.