No abstract

The extraction of light from the glass substrate of bottom emitting organic light emitting diodes by structured substrate surfaces is investigated by modelling and experiment. The angular intensity distribution emitted by the oled into the substrate is taken from measurement or calculation and the extraction enhancement by various microrefractive and scattering outcoupling structures is evaluated by Monte Carlo raytracing and experiment. Diagrams for the characterization of outcoupling structures are presented and discussed. It is concluded that the reflectance of the oled stack ultimately limits the amount of light which can be transferred from the oled through the substrate into air and that the transfer can be increased from about 50% for unstructured to about 80% and more for structured substrates and that the theoretical limit can be reached, e.g., with simple microlens structures. To further increase the efficiency of oleds the light guided and absorbed in the oled stack itself has to be tapped. The influence of the outcoupling structures on the angular light distribution emitted from the substrate into air is also studied.

The optical performance of interference filters depends on systematic and statistical variations of the thicknesses and indices of refraction of the layers that occur during production and use. Assuming that their distributions are known, the expected performance can be optimized as a function of the nominal layer thicknesses with the help of strategies that mimic biological evolution. This results in filter designs that are easier to manufacture and more robust to use. The method is illustrated for color shifts that are rather sensitive to layer thickness variations. Its scope is entirely general, and it could be applied to other tolerancing problems that arise in optical design.

Electrical Properties / Electrochemistry f Fuel Cells / Materials Properties / SemiconductorsWe present a planar cell design for Solid Oxide Fuel Cells (SOFC) which combines the ceramic materials of a solid electrolyte (Y-stabilized Zr02), cathode (LaSrMe03 with Me: Mn, Co and Cr), and anode (Ni-Cermet) with a metallic interconnection material, the so-called metallic bipolar plate. This metallic componentwhich functions as a mechanically stabilizing frame, as well as gas distributor and electrical connectorpossesses the advantages of much higher electrical and thermal conductivity when compared with the common ceramic interconnection material (LaCr03). This allows the construction of cell stacks with increased power density (> 100 kW/m3).

Based on the planar SOFC and SOE technology, a high temperature metal – air battery was operated at temperatures between 700°C and 800°C. It reached charging and discharging capacities of about 2 hours at power densities of more than 250mW/cm². A Siemens stack concept was developed and validated in numerous lab experiments as well as in several stack demonstrators of more than 1kW power output. The storage material is a proprietary development consisting of a iron/iron oxide combination which can be produced economically. It showed very low degradation rates of 1 - 2% in 1,000 charging / discharging cycles. More than 10,000 cycles were reached in 10x10 cm² short stacks. System efficiencies for the upper MW range of > 60% and a cycle life of about 10,000 cycles will be achieved.