The electronic structure of PC61BM film on clean Ag(100) and Ag(111) surfaces has been measured with photoemission spectroscopy. The interfaces are chemisorption. It is necessary to combine the two sub-interfaces model and the integer charge transfer model for thoroughly understanding the interfacial electronic structure. The electron injection barrier can then be determined without inverse photoemission measurements, and the PC61BM/Ag(111) system is found to be ohmic contact for electron transport. The analysis method should be applicable to many other organic/metal interfaces.
