title: Manipulating the charge transfer at CuPc/graphene interface by O₂ plasma treatments.
abstract: The manipulation of charge transfer at CuPc/graphene interface has been demonstrated by treating pristine graphene with O₂ plasma. As revealed by in situ ultraviolet photoelectron spectroscopy measurements, a much stronger interfacial charge transfer occurs when the pristine graphene is exposed to O₂ plasma prior to the growth of CuPc films, which is attributed to the increased work function of graphene after O₂ plasma treatment. Moreover, the highest occupied molecular orbital leading edge of CuPc locates at ∼0.80 eV below substrate Fermi level on O₂ plasma treated graphene, whereas it locates at ∼1.10 eV on pristine graphene. Our findings provide detailed information regarding the electronic structure at CuPc/graphene and CuPc/O₂ plasma treated graphene interfaces. The increased work function in combination with the relatively smaller energy offset between the highest occupied molecular orbital of CuPc and Fermi level of O₂ plasma treated graphene facilitates the extraction of holes at the interface, and hence paves the way for improving the performance of graphene-based organic photovoltaic cells.
authors.affiliation: Department of Physics, Hangzhou Normal University, Hangzhou 310036, China. phymaohy@gmail.com.
authors.forename: Hongying
authors.initials: H
authors.lastname: Mao
authors.forename: Fang
authors.initials: F
authors.lastname: Hu
authors.forename: Quan-Lin
authors.initials: QL
authors.lastname: Ye
authors.forename: Yifeng
authors.initials: Y
authors.lastname: Xu
authors.forename: Xuxin
authors.initials: X
authors.lastname: Yang
authors.forename: Bin
authors.initials: B
authors.lastname: Lu