Kazunobu Mameno

High Efficiency Stacked Organic Light-Emitting Diodes Employing Li2O as a Connecting Layer

We demonstrate the high-efficiency stacked organic light-emitting diodes (OLEDs) introducing new connecting layers. In the green stacked OLEDs, the external efficiencies increase proportionally to the number of the stacked units without suffering the decrease in power efficiency. The current, power and external efficiencies at 0.5 mA/cm2 of the stacked OLED with six stacked units (6-stacked OLED) have reached 235 cd/A, 46.6 lm/W, and 65.8%, respectively. Furthermore, we have applied the connecting layers to a white stacked OLED and fabricated an active-matrix full-color display with a low temperature polysilicon thin film transistor backplane. In the device, the current efficiency of the white 2-stacked OLED is enhanced by a factor of 2.2. The initial luminance drop is significantly suppressed for the white 2-stacked OLED compared to 1-stacked OLED. The proposed white stacked OLED technology can be applied to a full-color display for a practical use.

Full-color AMOLED with RGBW pixel pattern

Abstract— A full-color AMOLED display with an RGBW color filter pattern has been fabricated. Displays with this format require about one-half the power of analogous RGB displays. RGBW and RGB 2.16-in.-diagonal displays with average power consumptions of 180 and 340 mW, respectively, were characterized for a set of standard digital still camera images at a luminance of 100 cd/m2. In both cases, a white-emitting AMOLED was used as the light source, and standard LCD filters were used to provide the R, G, and B emission. The color gamuts of these displays were identical and the higher overall efficiency of the RGBW format results from two factors. First, a large fraction of a typical image is near neutral in color and can be reproduced using the white sub-pixel. Second, the white sub-pixel in an RGBW AMOLED display is highly efficient because of the absence of any color filter. The efficiency of these displays can be further enhanced by choosing a white emitter optimized to the target display white point (in this case D65). A two-emission layer configuration based upon separate yellow and blue-emitting regions is shown to be well suited for both the RGBW and RGB formats.

Reduction in Power Consumption for Full-Color Active Matrix Organic Light-Emitting Devices

The active matrix organic light-emitting diode (AMOLED) is expected to serve as next generation flat panels display with the outstanding features of wide viewing angle, vivid images, and quick response. For practical use of full-color AMOLEDs in mobile devices, it is essential to reduce the power consumption, which is generally higher than that of liquid crystal displays (LCDs). For this aim, a red, green, blue, and white (RGBW) pixel format combined with an RGB color filter array (RGBW format) with a common white emission layer (EML) has been developed. We find that the RGBW format can successfully reduce the power consumption of a full-color AMOLED by nearly half that of a conventionally filtered RGB pixel format. This improved power consumption is almost equal to the power consumption of a same-sized LCD. The RGBW format is a promising technique for the further reduction of the power consumption of a full-color AMOLED.

Evaluation of the gate oxide transformed by ion implantation

Abstract Ion implantation-induced damage to the gate oxide of antenna MOS capacitors has been investigated. It is confirmed that ion implantation into the MOS capacitors causes charge-induced damage and ion bombardment-induced damage. The degradation of the gate oxide due to ion implantation varies according to the relation between the projected range and the thickness of the polysilicon electrode. The mechanism of the oxide damage is discussed based on the results of current-voltage measurements and structural analyses by ESR and FTIR-ATR.

Developments in OLEDs with a co-dopant system for improved efficiency and stability

Development of RGB material has already reached the level of commercial products for full color displays devices such as digital cameras. However, the key challenges that still remain are improving luminance efficiency for lower power consumption and better stability. Applying a co-dopant into the EML is an effective way to adjust device performance. A large proportion of power is consumed in red sub-pixels in full-color displays with RGB sub-pixels. Previously we found that rubrene doping of red emitting layer improved the luminance efficiency and operational stability by enhancing the energy transfer from host material to emitting dopant. To increase the efficiency, a phosphorescent material as a red emitter was studied. We review the requirements for and characteristics of RGB OLEDs and the impact of co-doping systems on the performance of full-color displays.

The effect of surface electric and magnetic fields on negative charge-up during high-current ion implantation

The breakdown characteristics of a thin gate oxide during high-current ion implantation with an electron shower have been investigated by controlling the energy distribution of the electrons. Deterioration of the oxide has also been discussed with regard to the total charge during ion implantation in comparison with that of the TDDB (time dependent dielectric breakdown). Experimental results show that the high-energy and high-density electrons which concentrated in the circumference of the ion beam due to the space charge effect cause the degradation of the thin oxide. It is confirmed that eliminating the high-energy electrons by applying magnetic and electric fields lowers the electron energy at the water surface, thereby effectively suppressing the negative charge-up.<<ETX>>

31.5L: Late-News Paper: Development of a Combined Liquid Crystal and Fine Pitch Light Source Display (LFD)

We propose a novel display system that we call an LFD (combined liquid crystal and fine pitch light source display). In an LFD, an auxiliary light source patterned with a fine pitch is attached to a reflective liquid crystal display (LCD), and a light shield is formed on the observers side of the light source. A vertical alignment LCD (VA-LCD) is attached as the reflective LCD, and an organic light-emitting diode (OLED) is attached as the fine pitch light source. An LFD can produce bright, high-contrast images under any ambient light. We built a test sample and confirmed its display characteristics.