Correlation between interface energetics and open circuit voltage in organic photovoltaic cells

We have used ultraviolet and inverse photoemission spectroscopy to determine the transport gaps (Et) of C60 and diindenoperylene (DIP), and the photovoltaic gap (EPVG) of five prototypical donor/acceptor interfaces used in organic photovoltaic cells (OPVCs). The transport gap of C60 (2.5 ± 0.1) eV and DIP (2.55 ± 0.1) eV at the interface is the same as in pristine films. We find nearly the same energy loss of ca 0.5 eV for all material pairs when comparing the open circuit voltage measured for corresponding OPVCs and EPVG.