Effects of Surface Contaminants on Interface Dipole Formation of 8-hydroxyquinolinolato-lithium Layer

초록

To obtain efficient organic devices, minimizing the charge injection barrier between the metal electrode and organic layer is of great importance. For this, a fundamental understanding of the formation mechanism of the interface dipole that changes the work function of the electrodes necessary. In this study, different formations of the interface dipole of 8-hydroxyquinolinolato-lithium (Liq) on clean and contaminated metal surfaces was investigated using in situ ultraviolet photoelectron spectroscopy. On a clean Au surface, Liq induced a large interface dipole, and the work function significantly decreased, similar to other conducting electrodes. However, on a contaminated Ag surface, a negligible interface dipole was formed with the deposition of the Liq layer; thus, the work function hardly changed. This was caused by the decoupling between the electron wave functions of Liq and Ag by the contamination layer. Thus, to efficiently tailor the work function using a charge injection layer, the surface conditions of the electrodes should be carefully considered.

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