Energy Level Alignment of C_(60)/Ca Interface with Bathocuproine as an Interlayer Studied by Ultraviolet Photoelectron Spectroscopy

摘要

The energy level alignment of C_(60)/bathocuproine (BCP)/Ca interfaces as a function of BCP layer thickness has been studied by ultraviolet photoelectron spectroscopy. The results show that the energy level alignment is very sensitive to the BCP layer thickness. The energy levels of the lowest unoccupied molecular orbital of Ceo and BCP were found to be almost the same when the thickness of BCP interlayer is less than 1.6 nm. Such energy level alignment, which is favorable to the carrier transport, may be caused by an interaction between C_(60) and Ca, where Ca passed through the BCP interlayer and diffused to the C_(60) layer. The role and optimum design for BCP interlayer were discussed.