Electron acceptors based on alpha-position substituted PDI for OPV solar cells.

Authors

Abstract

The ortho-position functionalized perylene diimide derivatives (alphaPPID, alphaPBDT) were synthesized and used as the electron acceptors in nonfullerene organic photovoltaics. Due to the good planarity of ortho-position functionalized PDI, the alphaPPID and alphaPBDT show strong tendency to form aggregate because of their enhanced intermolecular pie-pie interaction. Moreover, they maintain the pure domains and the same packing order as in the pure film if they are blended with PBT7-TH and the SCLC measurement also shows the high electron mobility. The inverted OPVs employing alphaPDI-based compounds as acceptor and PBT7-TH as the donor give the highest PCE of 4.92 % for alphaPBDT based device and 3.61 % for alphaPPID based device, which is 39 % and 4 % higher than that for their counterpart betaPBDT and betaPPID. The charge separation study shows the more efficient exciton dissociation at interfaces between PDI based compounds and PBT7-TH. The results suggest that compared to beta-substituted ones, alpha-substituted PDI derivatives are more promising electron acceptors for OPV.