Influence of carbonaceous electrodes on capacitance and breakdown voltage for hybrid capacitor

This paper presents a new type of capacitor and deals with a hybrid approach where the advantages of two systems, dielectric capacitors and the ultracapacitor are combined. The objective is to increase the capacitance and the energy storage capability, while or at least preserving or decreasing the volume of the passive components. In this aim, the surface area and structural properties of ultracapacitor electrodes and the high dielectric strength of a polymer material are associated. The surface roughness of the carbonbased electrodes, namely (activated carbon—AC, and carbon nanotubes—CNTs), has a good impact on the capacitance. However, the surface roughness also depends on the composition of carbonaceous materials and so does the capacitance. Moreover, the choice of the dielectric material is the key parameter. The better the impregnation of the roughness is, the better is the increase of the capacitance. Since the final objective is to improve the electrical energy stored by the capacitor, the effect of surface roughness on the breakdown voltage is also evaluated

Organic light emitting device non-emissive area formation and inhibition

Ph.DDOCTOR OF PHILOSOPH

White-Light Generation and OLED Lifetime Issues.

This thesis presents experimental results and discussion regarding issues related to organic light-emitting devices (OLEDs). In particular, this thesis has three main focuses: the generation of white light from Förster transfer in blends of emissive polymer and methods used to characterize the efficiency of that transfer; low temperature, conformal, thin film encapsulation for organic devices; and the effect of a pulsed driving scheme on the lifetime of OLEDs. In the first research focus, a method is proposed to measure the efficiency of Förster energy transfer. The efficiency of Förster transfer has previously been studied in biological systems, but this thesis presents a method which may be used for systems of semiconducting polymers. In addition, this thesis presents a theoretical basis for comparing the efficiency of a Förster-blend-based white light emitter to a similar emitter with no Förster energy transfer in order to show that white light generation from Förster transfer does, indeed, increase emission efficiency. The latter two research efforts examine the effect of encapsulation and driving scheme on the growth rate of non-emissive dark regions in OLEDs and, as such, share similar experimental apparatus. The formation and growth of non-emissive dark regions have been a persistent problem in OLED fabrication. The results presented in this thesis show that the combination of proper encapsulation and driving method can effectively slow the growth of these non-emissive regions.Ph.D.Macromolecular Science & EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/60856/1/arjohn_1.pd

Effect of parylene layer on the performance of OLED

10.1016/S0026-2692(03)00238-6Microelectronics Journal354325-328MICE