The main process responsible for the luminance degradation in organic light-emitting diodes (OLEDs) driven under constant current has not yet been identified. In this paper, we propose an approach to describe the intrinsic mechanisms involved in the OLED aging. We first show that a stretched exponential decay can be used to fit almost all the luminance versus time curves obtained under different driving conditions. In this way, we are able to prove that they can all be described by employing a single free parameter model. By using an approach based on local relaxation events, we will demonstrate that a single mechanism is responsible for the dominant aging process. Furthermore, we will demonstrate that the main relaxation event is the annihilation of one emissive center. We then use our model to fit all the experimental data measured under different driving condition, and show that by carefully fitting the accelerated luminance lifetime-curves, we can extrapolate the low-luminance lifetime needed for real display applications, with a high degree of accuracy.

We report a bistable organic memory made of a single organic layer embedded between two electrodes, we compare to the organic/metal nanoparticle/organic tri-layers device [L.P. Ma, J. Liu, and Y. Yang, Appl. Phys. Lett. 80, 2997Lett. 80, (2002]. We demonstrate that the two devices exhibit similar temperature-dependent behaviors, a thermallyactivated behavior in their low conductive state (off-state) and a slightly "metallic" behavior in their high conductive state (on-state). This feature emphasizes a similar origin for the memory effect. Owing to their similar behavior, the one layer memory is advantageous in terms of fabrication cost and simplicity.

We present a technique to measure directly the extent of surface scattering in giant magnetoresistance (GMR) spin valves. By monitoring both resistance and magnetoresistance during deposition, we may quantify any discontinuous changes in electron scattering associated with the formation of a given surface. Our technique is applied to the case of noble metal overlayer deposition (Ag and Cu) on NiO/Co/Cu/Co spin valves. We find no evidence to support the establishment of a specularly reflecting surface.

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A new method suitable for the single core fluxgate magnetometer has been proposed. The method makes use of the coupling property of odd and even harmonics generated by the self-product of the induced voltage during the magnetization of ferromagnetic material by an external field superposed on the AC driving magnetic field. The power difference between the two half-periods of magnetization was expressed by the coupling of odd and even harmonics, which is proportional to the external field under the condition that He* Q HAC and HAC is constant, where HM and HAC are the external magnetic field'and AC driving tield amplitude respectively.