Akira Yokoi

27.5L: Late‐News Paper: Multiphoton Organic EL device having Charge Generation Layer

Novel structure of Multiphoton Emission (MPE) organic EL (OEL) device capable of exceeding 100% quantum efficiency was fabricated. The principle of the device is that a plurality of conventional OEL structure (emissive unit) are stacked and divided by Charge Generation Layer (CGL) that works as an injector of electron-hole pair upon voltage application. Tripled stacked MPE successfully achieved 48 cd/A for the emission from fluorescent green dye coumarin C545T.

27.1: Invited Paper: High Efficiency Organic EL Devices having Charge Generation Layers

We have developed organic EL (OEL) devices, in which extremely high quantum efficiency of over 100% can be obtained. In order to generate more than one photons per injected electron, “Charge Generation Layers (CGLs)” are placed between emissive units. At CGLs, electrons and holes are generated upon voltage application, and injected to the adjacent organic emissive layers. By using one CGL and two emissive units, quantum efficiency can be doubled compared to the conventional OEL device, and using two CGLs and three emissive units, quantum efficiency can be tripled. One of the OEL device using two CGLs and three emissive units, an extremely high efficiency of 48 cd/A (ca. 14% external) was obtained, which exceeds the so-called theoretical upper limit of 5%. Examples of such “multiphoton emission” (MPE) devices will be introduced.