Abstract

Within Philips Research, an extensive research program is being carried out on Organic Light-Emitting Diodes (OLEDs) for lighting applications. OLE Ds are potentially highly efficient large-area light sources, which can be used for general lighting applications in hitherto unprecedented ways, such as light-emitting flexible foils. In the past five years, the luminous efficacy of prototype white OLE Ds has shown a very fast increase, towards a present world-record value of 64 lm/W. In principle, there seems to be no fundamental obstacle towards 100 lm/W efficiency, beyond that of fluorescent lamps. However, in practice the ever-increasing complexity of the layer structure of OLE Ds now hampers progress towards that goal. For the further development of OLE Ds, the availability of an experimentally validated opto-electronic device model will be crucial. At present, such a model is not available. It has recently become clear that today’s “first generation” models, based on conventional understanding of transport and photo-physical processes, are insufficient for realistic OLED materials. Such models neglect several consequences of the disordered nature of the organic semiconductors used. In the seminar, the present status of advanced device simulations of transport and recombination in OLE Ds will be discussed, as well as experiments which validate this work. It will be shown that the current density in OLE Ds is expected to be highly filamentary, instead of uniform, and it will be argued that this might strongly affect the actual recombination rate across the device.