Full color displays

OLEDs are obviously able to produce light with virtually every color in the CIE chromaticity diagram but the optimum inexpensive method to manufacture a pixeiatcd full color display is not yet established. The difficulty lies in patterning OLED materials with standard photolithographic methods. Five schemes to achieve color have been suggested, as illustrated schematically in Figure 13-19. 

Electron-Deficient Polymers - Luminescent Transport Layers 16 Other Electron-Deficient PPV Derivatives 19 Electron-Deficient Aromatic Systems 19 Full Color Displays - The Search for Blue Emitters 21 Isolated Chromophores - Towards Blue Emission 21 Comb Polymers with Chromophores on the Side-Chain 22 Chiral PPV - Polarized Emission 23 Poly(thienylene vinylene)s —... 

Full Color Displays - The Search for Blue Emitters... 

Miyashita, S. et al. 2001. Full color displays fabricated by ink-jet printing. Proc. of Asia Display/IDW 01. pp. 1399-1402. 

FIGURE 1.20 Development history on monochrome (squares) and full-color displays (circles) at DuPont Displays (formerly UNIAX Corporation) solid symbols denote total pixel counts open symbols denote pixel density. 

A bewildering array of materials has been used as emitters in SMOLEDs since this early work on Alq3. In the following sections, we will present a brief review of host-guest emitter materials and give a perspective description of all the current state-of-the-art small molecule materials for emission at the three primary colors needed for full-color display applications. 

One of the most obvious markets for thin-film vapor-deposited organic materials is in flat panel displays [123], a market currently dominated by LCDs. Over the last two decades, a great improvement in the lifetime and efficiency of OLEDs have been achieved. OLED displays can already be found in simple applications such as automobile stereos, mobile phones, and digital cameras. However, to exploit the advantages of the technology fully, it is necessary to pattern the OLEDs to form monochrome, or more preferentially, full-color displays. This section will consider the difficulties involved in addressing such displays (either passively or actively) and the variety of patterning methods that can be used to produce full-color displays. 

Various ways of making full-color displays have been proposed. These are summarized in Figure 7.14. Perhaps the most obvious method is simply to fabricate red, green, and blue subpixels side by side on the same substrate (Figure 7.14a). Many companies have adopted this approach, e.g., Pioneer demonstrated a full-color QVGA (320 x 240 pixels) display at the Japan Electronics Show in 1998. Figure 7.15 is an example of a full-color display patterned using a side-by-side approach. 

Each of the techniques described above has unique strengths and weaknesses, and the optimum device structure for commercial full-color displays will also be heavily influenced by the ease with which it can be mass-produced. Currently full-color OLED displays have been manufactured commercially by using two of the above described techniques only, i.e., (a) side-by-side pixels deposited by high-precision shadow masking and (b) using white OLEDs and color absorption filters. 

These latest results demonstrate that decoupling deposition and micropatterning can be performed on industrial scale leading to sophisticated full-color displays. 

Since blue, green and red LEDs are now available, white light can be obtained by mixing colors. We have already discussed stacked LEDs which give full color display or... 

Francis Gamier [3, and references given therein] fabricated the first transistor using molecules of sexithiophene. The transistor could be twisted, bent or rolled without degrading its characteristics. Computers fabricated using these devices will work at less than one thousandth of the speed of those made with amorphous Si transistors. They would be useful in video displays and liquid-crystal displays. In active matrix displays, each pixel is controlled individually by a thin film transistor. A 50 cm full color display contains more than two million pixels. Organic transistors, considerably cheaper than the amorphous Si transistors being used at present, will be a boon to the manufacturers. 

When we apply diarylethenes to full color display, it is indispensable to synthesize yellow-developing compounds. We found that the color of the closed-... 

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