What is OLED?
Organic Light Emitting Diode (OLED) is a kind of light-emitting diode (LED) that uses organic compound to emit light. In OLED, the emissive electroluminescent (EL) layer is formed by a film of organic compound that emits light in response to the current flow.
OLED device is composed of two electrodes and several functional layers: electron transport layer (ETL), emitting layer (EML), and hole transport layer (HTL), etc. When a bias is applied between anode and cathode electrodes, electron and hole recombine in the EML and emit light in response to the current flow.
OLED device is composed of two electrodes and several functional layers: electron transport layer (ETL), emitting layer (EML), and hole transport layer (HTL), etc. When a bias is applied between anode and cathode electrodes, electron and hole recombine in the EML and emit light in response to the current flow.
Difference of OLED Manufacturing Methods
There are two types of method to manufacture OLED display; “evaporation technology” and “printing technology”. There are also two types of technologies to form EL layer; “White OLED” in which three layers are deposited in laminated structure to emit white color, and “RGB side by side” in which three different light emitting layers are deposited side-by-side through a fine mask. In the case of “White OLED” technology, color is produced by color filter that causes loss of 3/4 light, and color reproductivity contradicts light utilization efficiency. Actually major companies use “evaporation technology” in which EL layer is formed with vaporized EL material in vacuum chambers. It requires large vacuum chambers to accommodate panel and vapor deposition source and fine metal mask to form the EL layer on target points. Especially “RGB side by side” technology, it deposits each RGB layer individually and requires three times of fine mask. When the screen size becomes bigger or number of pixels rises, it becomes more difficult to align the mask. In addition, extremely low efficiency in material utilization and the difficulty in depositing uniform thin films are the issues for this technology. JOLED manufactures OLED displays using the highly production-efficient RGB printing method, which overturns the problems of the vapor deposition method. We also aim to share this manufacturing technology with our partners and establish it as an industry standard technology.
Vapor deposition method : White deposition
・Requires high degree of vacuum ・Requires mask
Vapor deposition method : 3-color deposition
・Requires high degree of vacuum ・Requires high-definition mask
Flexible display is a display that can be rolled, folded, or bended like a paper or cloth. With its ultra-thin and light profile, it can realize displays more freely designed or easy to store.
JOLED is researching and developing various flexible displays. A super light in weight, flexible and high performance display can be realized by replacing the conventional glass substrate to the plastic substrate, and using the oxide TFT. We are aiming at developing flexible OLED for practical use in near future.
JOLED is researching and developing various flexible displays. A super light in weight, flexible and high performance display can be realized by replacing the conventional glass substrate to the plastic substrate, and using the oxide TFT. We are aiming at developing flexible OLED for practical use in near future.
TAOS TFT Technology
To realize excellent performance of OLED, it is required high current flow to run for the thin film transistor (TFT).
Actually JOLED display uses low temperature poly-silicon (LTPS) TFT. LTPS TFT has good performance to run the high current flow but has same tasks such as non-uniform TFT performance due to the crystallization process and high manufacturing cost.
JOLED is now focusing on developing TAOS TFT (Transparent Amorphous Oxide Semiconductor) which has high electron mobility for high current flow and is uniformly formed on the large substrate.
We have developed a novel self-aligned top-gate TFT and realized superior reliability, by using a technology to passivate TFT electrode by metallic reaction. Also putting our unique correction circuit technology, we will realize high quality but reasonable OLED displays using our TAOS TFT.
Actually JOLED display uses low temperature poly-silicon (LTPS) TFT. LTPS TFT has good performance to run the high current flow but has same tasks such as non-uniform TFT performance due to the crystallization process and high manufacturing cost.
JOLED is now focusing on developing TAOS TFT (Transparent Amorphous Oxide Semiconductor) which has high electron mobility for high current flow and is uniformly formed on the large substrate.
We have developed a novel self-aligned top-gate TFT and realized superior reliability, by using a technology to passivate TFT electrode by metallic reaction. Also putting our unique correction circuit technology, we will realize high quality but reasonable OLED displays using our TAOS TFT.
