Exciton Dissociation and Electron Transfer at a Well-Defined Organic Interface of an Epitaxial C60 Layer on a Pentacene Single Crystal

The electron transfer of a well-defined single-crystalline organic P–N interface of the epitaxial layer of C60 on the surface of a single-crystalline pentacene (Pen-SC) was observed using time-resolved photoemission electron microscopy (TR-PEEM) with an optical pump and probe mode. The fine energy-tuning of the probe light and the selected-area detection of the photoelectrons, in addition to the PEEM detection of photoelectrons, allowed the measurement of the dynamics of electrons of rather insulating organic interfaces with a high signal-to-noise ratio, without suffering from the charging of the sample. After determination of the relaxation of the photogenerated electrons in Pen-SC via singlet fission through multiple-exciton states, two distinct electron transfer processes to the LUMO of the C60 layer were clearly observed by direct detection of the time evolution of the electrons in the LUMO of C60.