Masami Tsuchida

Organic EL cells using alkaline metal compounds as electron injection materials

Organic electroluminescent (EL) devices with multilayer structure were fabricated using alkaline metal compounds as the electron injection materials. We found that the EL cells using the alkaline metal compounds reduce the driving voltage and increase the quantum EL efficiency. In addition, these cells are made with good reproducibility compared with the cells using aluminum and lithium alloy cathode.

Flexible OLED displays using plastic substrates

Organic light-emitting diodes (OLEDs) displays using plastic substrate have many attractive features. They are ultrathin and light, in addition, it will be realized the flexible display to utilize the flexibility of the substrate. The key issue in achieving such displays is how to protect OLEDs from moisture and oxygen. We developed a barrier film on a plastic substrate and a passivation film on the OLED device itself. As a result, the device showed good emission characteristics after storage, and its characteristics were almost the same as those of a device fabricated on a glass substrate. We also developed a 3-in full-color flexible OLED display.

An organic LED display exhibiting pure RGB colors

Abstract A full color 5.2-in. 1/4 video graphics array (VGA) passive-matrix organic light emitting diode (OLED) display has been developed. The display features 320 (×3)×240 pixels with an equivalent pixel size of 0.33×0.33 mm 2 , white peak luminance of over 150 cd/m 2 , and power consumption of 6 W. It uses a cathode patterning method with electrically insulated cathode separators and an RGB emitters selective deposition method with a high accuracy mask moving system. Furthermore, we have achieved pure RGB colors as well as high luminance from the cells by applying the optical interference effects. The display can display high resolution video rate pictures with virtually the same quality as a CRT can offer.

Stability characteristics of quinacridone and coumarin molecules as guest dopants in the organic LEDs

Abstract During stability testing of organic light-emitting diodes (LEDs), a large amount of current (charge) injected into the LED cells raises the cell temperature quite a bit. The morphology of the organic thin films may have changed and formed the excimer and exciplex between different molecules. To keep the excimer and exciplex from forming during the driving test, the organic molecules should give steric hindrance by bulky substituents so that they do not move in the films. Moreover, the molecular structures should not have reactive chemical bonds. A cell doped with quinazoline or quinacridone, with bulky substituents at the imino group side in the Alq host, has a longer operational half-lifetime than that of a cell with quinacridone doping. A cell doped with coumarin derivative, which has no imino and carbonyl, also has a longer operational half-lifetime than that of a cell doped with coumarin with imino and carbonyl.

21.1: Invited Paper: 3-inch Full-color OLED Display using a Plastic Substrate

We developed a full-color Organic Light Emitting Diode (OLED) display on a plastic substrate. The display area is a 3- inch diagonal area with 160 × RGB × 120 pixels. Silicon oxynitride (SiON) was used as a moisture barrier film on the substrate and silicon nitride (SiN) as a passivation film on the device. The display was approximately 0.2 mm thick, weighted approximately 3 g, and it was bendable.

5.1: Active Matrix Organic Light Emitting Diode Panel using Organic Thin-Film Transistors

By using organic thin-film transistors with pentacene as the active organic layer, active matrix organic light emitting diode panel has been developed. The number of pixels in the panel is 8 × 8, and each pixel is driven by switching and driving transistors. We confirmed 16 gray scales representation by means of an analog driving method.

Organic LED full‐color passive‐matrix display

— A full-color 5.2-inch 1/4-VGA passive-matrix organic LED display has been developed, adopting selective deposition for the different emitting materials. The display features 320 (×3) × 240 pixels with an equivalent pixel size of 0.33 × 0.33 mm, white peak luminance of over 150 cd/m2, and power consumption of 6 W.

Active Matrix Driving Organic Light-Emitting Diode Panel Using Organic Thin-Film Transistors

We developed an active matrix driving organic light-emitting diode (OLED) panel on a glass substrate using two organic thin-film transistors (OTFTs) per pixel, a switching OTFT and a driving OTFT. The OTFTs are bottom contact structures with the high-dielectric constant gate insulator tantalum oxide (Ta2O5, relative dielectric constant of 23) produced by anodization in ammonium adipate solution and with pentacene as the active layer. The W/L (where W and L are the OTFTs channel width and length, respectively) was 400 µm/10 µm for the switching OTFTs and 680 µm/10 µm for the driving OTFTs. The characteristics of the OTFTs were improved by treating the Ta2O5 surface with hexamethyldisilazane (HMDS), so that the field-effect mobility was 2.0×10-1 cm2 V-1 s-1 and the current on/off ratio was 105. A green phosphorescent dopant, tris(2-phenylpyridine)iridium [Ir(ppy)3], was used for the OLED layer. The panel had 8×8 pixels and the aperture ratio was 27%. We confirmed a 16-gray-scale representation and a luminance of 400 cd/m2.

Organic LED Full Color Passive-Matrix Display

A full color 5.2 inch 1/4VGA passive-matrix organic LED display has been developed adopting selective deposition for the different emitting materials. The display features 320 (× 3) × 240 pixels with an equivalent pixel size of 0.33 × 0.33 mm2 white peak luminance of over 150 cd/m2 and power consumption of 6 W.