Bisadducts of C70 as Electron Acceptors for Bulk Heterojunction Solar Cells: A Theoretical Study

Abstract

In the present study, we have used density functional molecular orbital calculations to investigate the energy levels of the frontier orbitals of novel bisadducts of Phenyl-C71-Butyric-Acid-Methyl Ester (bis[70]PCBM) in an attempt to verify if they can be used as electron acceptor in polymer-fullerene solar cells. C70 derivatives are promising materials for these devices because they have a stronger and broader absorption compared to C60 ones, and they can improve the current output of the corresponding polymer-fullerene solar cells. The calculated LUMO levels for the bis[70]PCBM isomers are higher compared to the monoadduct already used as acceptor in such devices. Since the open circuit voltage (Voc) for devices with ohmic contacts is proportional to the difference between the HOMO of the donor polymer and the LUMO of the acceptor, these bisadducts can increase the Voc of polymer solar cells having poly(3-hexylthiophene) as donor.