Source: {"pile_set_name": "USPTO Backgrounds"}

1. Field of the Invention
The present invention relates to an organic light-emitting device, and more particularly, to an organic light-emitting device with low driving voltage and excellent light-emitting efficiency.
2. Description of the Related Art
Conventional display devices are being replaced with portable thin flat-panel display devices. Electroluminescent light-emitting display devices are self-luminous flat-panel display devices, and have advantages such as wide viewing angles, excellent contrast, and fast response speed. Thus, electroluminescent light-emitting display devices are being highlighted as next-generation display devices. Furthermore, organic light-emitting display devices, which include light-emitting layers made out of organic materials, have higher brightness, lower driving voltage, and quicker response speed as compared to inorganic light-emitting display devices. Also, organic light-emitting display devices can be polychromic.
An organic light-emitting display device includes an organic light-emitting device. An organic light-emitting device includes an anode, a cathode, and an intermediate layer arranged between the anode and the cathode. The intermediate layer includes an organic light-emitting layer and another organic material layer. A voltage difference is applied across the organic light-emitting layer via the anode or cathode causing the organic light-emitting layer to emit visible light.
Here, the organic material layer in the intermediate layer generally includes a plurality of layers. The plurality of organic material layers provide for easy transportation and implantation of electric charges into the organic light-emitting layer.
However, it is not easy to combine a plurality of organic material layers for high light-emitting efficiency, optimized charge balance, and long lifetime. In other words, there are limits to the extent to which the properties of an organic light-emitting device can be optimized by mutually combining a plurality of organic material layers due to the types and characteristics of the organic material layers. The electron transport layer can include only three layers.