Organic light-emitting device comprising buffer layer and method for fabricating the same

Abstract

Disclosed herein are an organic light-emitting device having a structure formed by the sequential deposition of a substrate, a first electrode, at least two organic layers and a second electrode, in which the organic layers include a light-emitting layer, and one of the organic layers, which is in contact with the second electrode, is a buffer layer comprising a compound represented by the following formula 1, as well as a fabrication method thereof: wherein R1 to R6 have the same meanings as defined in the specification. The buffer layer makes it possible to minimize or prevent damage to the organic layer, which can occur when forming the second electrode on the organic layer.

Description

TECHNICAL FIELD [0001] The present invention relates to an organic light-emitting device and a method for fabricating the same. More particularly, the present invention relates to an organic light-emitting device including a layer for preventing an organic layer from being damaged when forming an electrode on the organic layer in a process of fabricating the organic light-emitting device, and a method for fabricating the same. BACKGROUND ART [0002] Organic light-emitting devices (OLED) are generally composed of two electrodes (an anode and a cathode) and at least one organic layer located between these electrodes. When voltage is applied between the two electrodes of the organic light-emitting device, holes and electrons are injected into the organic layer from the anode and cathode, respectively, and are recombined in the organic layer to form excitons. In turn, when these excitons decay to their ground state, photons corresponding to the energy difference are emitted. By this prin...

AI Technical Summary

Benefits of technology

[0031] According to the present invention, damage to the organic layer, which can occur when forming an electrode on the organic layer, can be prevented by the buffer layer comprising the compound of formula 1 below. By this, an organic light-emitting device having a structure formed by the sequential lamination of a substrate, a cathode, organic layers and an anode can be fabricated without damage to the organic layer, which can occur when forming the electrode on the organic layer.

Problems solved by technology

When the active matrix organic light-emitting device displays having this backplane are fabricated to have the bottom emission structure, a portion of light emitted toward the substrate is blocked by the TFT array, resulting in a reduction in the effective display aperture ratio.

This problem becomes more severe when pluralities of TFTs are given to one pixel in order to fabricate more elaborate displays.

For this reason, if the cathode is made of this oxide film, the injection of electrons from the cathode into the organic layer becomes difficult, resulting in a great increase in the operating voltage of the organic light-emitting devices and deteriorations in important device characteristics, such as light emission efficiency.

In a process of fabricating the organic light-emitting device with the above-described inverted structure, if the electrode located on the organic layer is formed of a transparent conductive oxide film, such as IZO or ITO, by the use of resistive heating evaporation, the resistive heating evaporation will cause the collapse of the inherent chemical composition ratio of the oxide due to, for example, thermal decomposition during a thermal evaporation procedure.

This will result in the loss of characteristics, such as electrical conductivity and visible ray permeability.

However, if the electrode is formed on the organic layer by techniques such as sputtering, the organic layer can be damaged due to, for example, electrically charged particles present in plasma used in the sputtering process.

Thus, the physical properties of the organic layer can be deteriorated by particle bombardment on the organic layer, resulting in deterioration of electron or hole injection and transport characteristics and light emission characteristics.

Particularly, organic materials consisting mainly of covalent bonds of C and H, and thin films made of these materials, are generally very weak against plasma during a sputtering process, compared to inorganic semiconductor materials (e.g., Si, Ge, GaAs, etc.) and, once damaged, the organic materials cannot be returned to their original state.

However, as most of the above-described methods result in a very low deposition rate, the processing time of the sputtering step becomes very long, resulting in a significant reduction in productivity throughout a batch process for fabricating the organic light-emitting device.

Furthermore, even in an instance when the sputtering process has a low deposition rate as described above, the possibility of particles having high kinetic energy reaching the surface of the organic layer still exists, and thus, it is difficult to effectively prevent sputtering damage to the organic layer.

However, the Mg:Ag metal film has shortcomings in that the metal film is lower in visible ray permeability than ITO or IZO and also its process control is somewhat complicated.

This deteriorates device characteristics, such as the charge injection characteristic and electric current efficiency of the organic light-emitting device.

Furthermore, CuPc has large light absorption in the visible ray region, and thus, increasing the thickness of the CuPc film leads to rapid deterioration of the device performance.

However, this method for preventing sputtering damage has problems in that an additional thin metallic film is required and process control also becomes difficult.

However, the electron injection characteristic is improved only when the method is used in a device in which the cathode is used as a top contact electrode, while the electron injection characteristic is very poor when the method is used in a device having an inverted structure in which the cathode is used as a bottom contact electrode.

However, the structure has a disadvantage that the fabricating process is very complicated.

However, the method also has a problem in the process because a new layer must be used.

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