Combined spectroscopic characterization of electron transfer at hybrid CuPcF16/GaAs semiconductor interfaces

We characterize photoinduced charge injection at the interface between a fluorinated copper phthalocyanine (CuPcF16) film deposited over a GaAs(100) wafer by means of pump-probe spectroscopy combined with ultraviolet photoemission spectroscopy (UPS) and electromodulated transmission spectroscopy. UPS characterization of the hybrid interface demonstrates that the CuPcF16's lowest unoccupied molecular level (LUMO) is almost aligned with the GaAs conduction band. Upon photoexcitation of the hybrid interface with 150 fs pulses we observe an efficient photoinduced electron transfer from CuPcF16 to GaAs. The evolution of interfacial CuPcF16 charges appear to be strongly influenced by energy level alignment at the GaAs/CuPcF16 heterojunction.