Unveiling the Electronic Structure of ZnO–C 60 Core–Shell Quantum Dots: The Origin of Efficient Electron Transport

The electronic structure of ZnO core–C 60 shell (ZnO@C 60 ) quantum dots (QDs) was investigated with the help of model interface analysis between ZnO QDs and C 60 using in situ ultraviolet and X-ray photoelectron spectroscopy measurements. To form the ZnO QDs/C 60 interface in situ, a vacuum-integrated electrospray deposition technique was employed to simulate the electronic interactions between ZnO QDs and C 60 upon the formation of a ZnO@C 60 core–shell structure. Photoelectron spectra of ZnO QDs/C 60 interface formation were compared with those of ZnO@C 60 QD and pristine ZnO QD films. The results revealed that ZnO QDs and C 60 interacted via electron transfer leading to the change in ionization energy of the surface C 60 . This induced a negligible energy barrier between the lowest unoccupied molecular orbital level of C 60 and the conduction band minimum of ZnO, which led to efficient electron transport through the ZnO@C 60 QDs.