Hideo Satoh

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.

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.

Development of an advanced high efficiency electro-emission device

In this article, we describe the improvement in cold emission characteristics of a device termed HEED (high efficiency electro-emission device) by optimizing the emission site structures. The advanced HEED consists of a bottom electrode, a Si layer, a SiOx layer, a top electrode, and a carbon layer. The electron emission properties were significantly improved by appropriately arranging emission sites of “dimplelike” forms with a diameter of 1 μm on the device surface. The applied voltage was significantly lowered to 20 V (1/5 of that in the previously reported HEED), and a high emission current density of 1.8 mA/cm2 was obtained at a applied voltage of 20 V with an electron emission efficiency of 1% under a pulse operation. The energy distribution measurement of emitted electrons showed that the device emits considerably high-energy electrons as compared with conventional field emitters. Using this emitter as an excitation source, a 4 in. prototype flat display panel has been fabricated with a vacuum spac...

Fabrication of active-matrix high-efficiency electron emission device and its application to high-sensitivity image sensing

Practical advantages of an advanced high-efficiency electron emission device (HEED) (low-voltage operation, relatively simple structure, and availability for large-area applications) are further confirmed by its compatibility with active-matrix drive configuration. The fabricated HEED array has been applied to a high-sensitivity image sensing tube with a target of high-gain avalanche rushing amorphous photoconductor (HARP). It is demonstrated that a prototype 256×192pixel active-matrix HEED array operates well as an effective probe for high-resolution image pickup in combination with a HARP target. The advanced HEED array is promising for development of next-generation image sensor with ultrahigh sensitivity and high definition.

Characterization of an advanced high-efficiency electron emission device

As previously reported, the emission characteristics of metal-insulator-semiconductor (MIS) electron emission devices could be significantly improved by introducing microdimple structures into the emission sites. In this paper, we describe the characteristics of efficient cold electron emitters from a viewpoint of application to flat panel display (FPD). First, the forming operation for the device to activate the dynamic emission is discussed on a basis of the experimental analyses of the electrical properties and output electron energy spectra. Next it is demonstrated that the device has some desirable features as an excitation source of FPD: a high emission current density, a low operation voltage, emission uniformity, and stable emission with small angle dispersion. It is also shown from the result of lifetime evaluation that the device shows a half-life of 3000 h, and that the deteriorated emission can be recovered by the dc reactivation treatment.

High-current emission from active-matrix HEED (high-efficiency electron emission device) - application to image sensing

A 256 /spl times/ 192 pixels active-matrix cold electron emitter array with integrated scan driver circuits is developed. The basic structure of the electron emitter is almost the same as that of an advanced HEED (high-efficiency electron emission device) previously reported. The emission current density of the active-matrix HEED has been enhanced more than 100 times compared to that of the advanced HEED under the passive operation mode. It is demonstrated that the developed emitter can be applied to flat image sensing with a high-gain avalanche rushing amorphous photoconductor (HARP) target.

Characterization of an advanced HEED (High Efficiency Electron-emission Device)

We recently developed a new-type cold cathode termed HEED (High-Efficiency Electron-emission Device) based on the Metal-Insulator-Semiconductor (MIS) diode. It has been shown that by arranging the device and surface structures the emission characteristics can be significantly improved. Using the advanced HEED as an excitation source, a 4-inch prototype flat panel display has been fabricated on a glass substrate. The panel operates well with a practical brightness at a relatively low driving voltage. The occasional reactivation technique is very effective to prolong the operation life of this device.

Development of an advanced Heed (High Efficiency Electro-Emission Device)

It is shown that the emission characteristics of a previously reported MIS-type electron emission device termed HEED (High Efficiency Electro-Emission Device) can be significantly improved by appropriate arrangements of the emission site structures. Using this emitter as an excitation source, a 4-inch prototype flat panel display has been fabricated on a glass substrate. The panel operates well at a practical brightness of 2000 cd/m/sup 2/.