Efficient organic solar cells with helical perylene diimide electron acceptors

We report an efficiency of 6.1% for a solution-processed non-fullerene solar cell using a helical perylene diimide (PDI) dimer as the electron acceptor. Femtosecond transient absorption spectroscopy revealed both electron and hole transfer processes at the donor–acceptor interfaces, indicating that charge carriers are created from photogenerated excitons in both the electron donor and acceptor phases. Light-intensity-dependent current–voltage measurements suggested different recombination rates under short-circuit and open-circuit conditions.