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 C-60 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 C-60 layer were clearly observed by direct detection of the time evolution of the electrons in the LUMO of C-60.