When a thin layer of bathocuproine (BCP) is inserted between the metal electrode and organic layer of organic semiconductor device, the electron injection/collection efficiency at the interface is significantly improved. However, the mechanism of electron transport through the BCP layer has not been clarified yet. In this study, we directly observed the unoccupied electronic states of the Ag/BCP interface using low-energy inverse photoemission spectroscopy. The result shows that Ag strongly interacts with the BCP molecule and the lowest unoccupied molecular orbital (LUMO) level of the Ag-BCP complex aligns with the Fermi level indicating that the electron transport occurs through the LUMO level of the complex. With the aid of DFT calculation, we identify the reaction product.
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