1. Field of the Invention
The present invention relates to a carbazole derivative and an organic light emitting device using the same.
2. Description of the Related Art
An organic light emitting device is a device in which a thin film including a fluorescent organic compound or a phosphorescent organic compound is interposed between an anode and a cathode. Further, electrons and holes are injected from the respective electrodes to generate exciton of the fluorescent compound or the phosphorescent compound, whereby light is emitted when the exciton return to a ground state is utilized.
According to a study at Eastman Kodak company in 1987 (Appl. Phys. Lett. 51, 913 (1987)), there is reported a device having a function-separation type two-layer structure using ITO as an anode, a magnesium-silver alloy as a cathode, an aluminum quinolinol complex as an electron transporting material and a light emitting material, and a triphenylamine derivative as a hole transporting material. There has been reported a light emission of approximately 1,000 cd/m2 at an applied voltage of approximately 10 V.
Recent progress of an organic light emitting device is remarkable, and the characteristics of the device enable a light emitting device with a high luminance at a low applied voltage, a variety of emission wavelengths, high-speed responsiveness, thin and light weight. From this fact, it is suggested that the device have potential to find use in a wide variety of applications.
However, the present situation calls for optical output with even higher luminance or high conversion efficiency. In addition, many problems still remain to be solved regarding durability against the change over time due to long-term use, deterioration caused by atmospheric gas containing oxygen, moisture, or the like. Further, when considering application to a full color display, the present art is still insufficient against problems relating to the needs for light emission of blue, green, and red with a high color purity.
To solve the above-mentioned problems, there is proposed to use a carbazole derivative as a material for the organic light emitting device. As examples of the organic light emitting device using the carbazole derivative, there are given devices disclosed in “Journal of the American Chemical Society (2004), 126(19), 6035-6042,” and “Bulletin of the Korean Chemical Society (2004), 25(8), 1202-1206.”