1. Field of the Invention
The present invention relates to electronic devices having an n-type organic compound layer in an electrode for hole injection or hole extraction. More particularly, the present invention relates to electronic devices capable of lowering the energy barriers for hole injection or hole extraction.
2. Description of the Related Art
Electronic devices such as solar batteries, organic luminescence devices, or organic transistors include two electrodes and an organic compound disposed between the electrodes. Solar batteries, for example, generate electricity by using the electrons and holes separated from exciton generated in organic compound layers in response to solar energy. Organic luminescence devices inject electrons and holes into the organic compound layer from two electrodes to convert electric currents into visible light. Organic transistors transport the holes or electrons generated in organic compound layers between a source electrode and a drain electrode in response to the voltage applied to a gate. Electronic devices may further include an electron/hole injection layer, an electron/hole extraction layer, or an electron/hole transporting layer in order to improve performance.
The interface between electrodes having a metal, a metal oxide, or a conductive polymer, and an organic compound layer, however, is unstable. An external heat, an internally generated heat, or the electric field applied to the electronic devices could adversely affect the performance of electronic devices. A driving voltage of electronic devices could be increased by the conductive energy difference between an electron/hole injection layer or an electron/hole transporting layer and an organic compound layer. Therefore, it is important to stabilize the interface between the electron/hole injection layer or the electron/hole transporting layer and the organic compound layer, as well as minimizing the energy barrier for injecting/extracting electron/hole into/from electrodes.
Electronic devices have been developed to control the energy difference between electrodes and an organic compound layer disposed between the electrodes. In a case of organic luminescence devices, an anode electrode is controlled to have a Fermi energy similar to the Highest Occupied Molecular Orbital (HOMO) energy of a hole injection layer, or a compound having the HOMO energy similar to the Fermi energy of the anode electrode is selected for the hole injection layer. Because the hole injection layer should be selected in view of the HOMO energy of the hole transporting layer or light emitting layer, in addition to the Fermi energy of the anode electrode, there is limitation in choosing compounds for the hole injection layer.
Therefore, a method for controlling the Fermi energy of an anode electrode has been generally adopted in manufacturing organic luminescence devices. Compounds for anode electrode, however, are limited. Organic transistors, for example, have used gold or novel metals for a source/drain electrode. Such gold or novel metals, however, are expensive and hard to process using industrial methods, thus restricting their application and structure in organic transistors.