Operational degradation

Identify the causes of process trends, e.g., external load disturbances, equipment faults, operational degradation, operator-induced mishandling. 

As discussed in Section 7.1, NPB Alq devices may not be representative of many different OLED device structures. It is therefore natural to ask whether the role deep traps play in operational degradation is unique for the NPB Alq devices. To answer this question, we examined a diverse set of fluorescent and phosphorescent OLED devices spanning more than two orders of magnitude difference in stability. The results are summarized in Table 7.1 and the following is noteworthy. Despite the structural and functional dissimilarities in the experimental set, the operation-induced accumulation of fixed positive charge densities and correlation with luminance loss were invariably observed. Although we observed some nonlinearity in luminance-charge... 

Despite the potential significance of shallow traps in the operational degradation of OLED devices, there are no established general techniques for their effective detection and measurement in such an environment. The application of methods, such as electron spin resonance [43], electrically detected magnetic resonance [44], and charge modulation spectroscopy [45,46], is hindered by their limited sensitivities and selectivities in operationally degraded OLED devices. 

The monopolar devices with predominantly hole current were constructed by placing a thin Alq layer between NPB layers, which act as hole-transport and electron-blocking layers. The nearly monopolar characteristic of such devices was confirmed by observing only weak electroluminescence, which also precluded using it to evaluate the extent of operational degradation. On the other hand, the differences in absorption spectra of Alq and NPB permitted the separate photoexcitation of the thin Alq layer with 442 nm Hg line. In situ measurements revealed continuously decreasing photoluminescence... 

Kondakov, D. Y., Lenhart, W. C., and Nichols, W. F. 2007. Operational degradation of organic light-emitting diodes Mechanism and identification of chemical products. J. Appl. Phys. 101 024512. 

The fleet model was obtained under the assumption that time to failures and (intrinsic) repair times of the modules are mutually independent random variables. The number and the states of the circulating trams are identified via the pair d, c, being d the number of operating degraded trams and c the number of failed trams in queue at the maintenance shop. 

Failure to cease operation at a prescribed time Loss of output or failure during operation Degraded output or operational capability... 

Mechanical stability. To rednce the contact resistance, to have the necessary compression pressure for the seahng of the cells, and to resist different pressures of the media, the plate must be mechanically stable. Changing strain results from different pressures and different temperatures between idhng and full-load operation. Degradation by changing mechanical strain has to be avoided by proper dimensioning of the materials. 

Does the safe state involve continued operation, degraded operation, or shutdown entirely ... 

S.3.3.2 Degradation of DCB under Pressure-Induced Operation Degradation of DCB is conducted under pressure-induced condition. As the solution convectively passed through the membrane by applying pressure at the cell reservoir, mass transfer of... 

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