Operation device structures

The utility and importance of multi-layer device structures was demonstrated in the first report of oiganic molecular LEDs [7]. Since then, their use has been widespread in both organic molecular and polymer LEDs [45, 46], The details of the operating principles of many multi-layer structures continue to be investigated [47—49], The relative importance of charge carrier blocking versus improved carrier transport of the additional, non-luminescent layers is often unclear. The dramatic improvements in diode performance and, in many cases, device lifetime make a detailed understanding of multi-layer device physics essential. 

The paper is oiganized to describe, first, the materials that have been used in OLEDs, then the device structures that have been evaluated. After a description of the methods used to characterize and evaluate materials and devices, we summarize the current stale of understanding of the physics of device operation, followed by a discussion of the mechanisms which lead to degradation and failure. Finally, we present the issues that must be addressed to develop a viable flat-panel display technology using OLEDs. Space and schedule prevent a comprehensive review of the vast literature in this rapidly moving field. We have tried to present... 

In this section the electronic structure of metal/polymcr/metal devices is considered. This is the essential starting point to describe the operating characteristics of LEDs. The first section describes internal photoemission measurements of metal/ polymer Schottky energy barriers in device structures. The second section presents measurements of built-in potentials which occur in device structures employing metals with different Schottky energy barriers. The Schottky energy barriers and the diode built-in potential largely determine the electrical characteristics of polymer LEDs. 

For the planning of a multipurpose plant one has to map the structure of a master recipe to the detailed device structure of the plant with regard to a given time in the future. This process can be done automatically, e.g., with the SAP ERP system where it is called convert. The result is a process order as a concretization of a master recipe. A process order tells the production operator at which time and on which device a given batch production step has to be executed. This simple conversion can result in a situation where a selected device is already allocated to a different process order at the given time, thus the production plan may not be feasible. 

The operating principles of the reviewed interferometers are well studied. However, by no means these devices are matured. For example, a mode-selective, wavelength-independent and environmental-resistant 3-dB core-cladding mode coupler is yet to be found to construct an ideal CCMI. As technology advances and research continues, we expect that more device structures will be explored and new methods will be investigated to fabricate these devices. Although the applications of these two types of sensors are yet to be explored, it is almost certain that they will find their way into real-world applications in the future. 

Spiro-FPAl/TPBI/Bphen Cs/Al. A very low operating voltage of 3.4 V at luminance of 1000 cd/m2 was obtained, which is the lowest value reported for either small-molecule or polymer blue electroluminescent devices. Pure blue color with CIE coordinates (0.14, 0.14) have been measured with very high current (4.5 cd/A) and quantum efficiencies (3.0% at 100 cd/m2 at 3.15 V) [245]. In another paper, Spiro-FPA2 (126) was used as a host material with an OLED device structure of ITO/CuPc/NPD/spiro-FPA2 l%TBP/Alq3/LiF that produces a high luminescent efficiency of 4.9 cd/A [246]. 

This strategy, although it can be used to achieve white emission, leads to a device fabrication process, which is tedious and where the emission color is sensitive to the operating voltage and device structure parameters such as active layer thickness and doping concentration. 

Vapor resist has been used to produce 8 nm structures (52) and operating devices with dimensions of 25 nm (Figure 15) (55), but suffers from similar resolution constraints as conventional resists. 

There are two possible approaches towards making feasible devices. One approach is to develop device structures that need smaller coefficients to operate, e.g lossy Fabry-Perot cavities (8), the other approach is to trade-off some of the speed and low loss in current organics for larger responses, for instance by tuning into resonances. In this paper we will explore the latter route and show how this can be achieved in some materials whilst maintaining, at acceptable levels, the critical figures of merit relating the nonlinear refraction to linear loss and two photon absorption to nonlinear refraction. 

One important aspect of the double-cell device is that, for proper operation of the device, the two cells must be electrically decoupled. This can be accomplished by proper design of the device structure. 

The observation of luminescence from laser dyes by ECL methods offers the possibility of using this approach to create dye lasers. A laser operating by ECL would not require an additional pump laser, and enhanced power, tunability, and wavelength selection are additional factors. While the pumping rate achieved by ECL previously has been two orders of magnitude lower than the optimal, Horiuchi et al. have reported a device structure designed to enhance the ECL efficiency and realize laser action driven by ECL [67], This experiment is illustrated in Fig. 14. A pair of sputter-deposited platinum film electrodes were positioned facing each other 2 to 7 microns apart. One electrode functioned... 

Y onventional wisdom usuaUy places the upper limit for the fundamental mode of quartz TSM devices between 10 and IS MHz. Alternative device structures, however, can achieve a fundamental fiequency significantly greater than tins, with operating frequencies of up to 100 MHz. 

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