Ultrafast charge-transfer processes at an oriented phthalocyanine/C60interface

The ultrafast dynamics at a well-characterized $\text{CuPc}/{\text{C}}_{60}$ organic photovoltaic heterojunction have been directly measured with time-resolved two-photon photoemission (TR-2PPE). Phthalocyanine/${\text{C}}_{60}$ donor-acceptor interfaces, characterized in detail via scanning tunneling microscopy, provide model systems for studies of critical charge separation and recombination processes that determine device performance. TR-2PPE studies of copper phthalocyanine $(\text{CuPc})/{\text{C}}_{60}$ interfaces reveal ultrafast charge separation and provide evidence for recombination via low-lying CuPc triplet levels.