Application of OLEDs in Flat-Panel Displays

In this section, we provide a brief introduction to the field of display engineering and the human-factors issues which dictate display design. We then assess how OLEDs measure up to the criteria necessary to achieve a commercially successful display technology. But first, we take a short detour to lay out the language used by display engineers and to provide a means of translating from the scientific units that we have used up to now. 

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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. 

OLEDs are nowadays the most important type of light source for artificial lighting, making them potential candidates in the development of full-color flat panel display devices. Challenging problems to be addressed are emission color, emission efficiency and device lifetime. The emission color problem results from the broad emission bands exhibited by electroluminescent devices containing organic emitting layers, since pure and sharp emission bands from these materials, a requisite for display applications, are... 

Another conducting polymer that has found commercial application is poly(3,4-ethylenedioxythiophene), PEDOT, which is marketed as a dispersion that contains poly(styrene sulfonate). This polymer dispersion is used in the manufacture of organic light-emitting diodes (OLEDs), which are materials that emit light when an electric current is applied to them (Figure 27.13). OLEDs are used for flat panel displays in televisions and cellular telephone displays. 

Organic light-emitting diodes (OLEDs) based on thin conjugated polymer films have attracted much interest recently because of their possible application in large-area flat-panel displays [1]. The use of double layer structures employing a hole transport layer (HTL) leads to improved device performance (Fig. 1). 

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