Covalently Bound Clusters of Alpha-Substituted PDI-Rival Electron Acceptors to Fullerene for Organic Solar Cells

A cluster type of electron acceptor, TPB, bearing four alpha-perylenediimides (PDIs), was developed, in which the four PDIs form a cross-like molecular conformation while still partially conjugated with the BDT-Th core. The blend TPB:PTB7-Th films show favorable morphology and efficient charge dissociation. The inverted solar cells exhibited the highest PCE of 8.47% with the extraordinarily high Js, values (>18 mA/cm(2)), comparable with those of the corresponding PC7IBM/PTB7-Th-based solar cells.