AG Melzer
Centre for Advanced Materials
Heidelberg University

Im Neuenheimer Feld 252 / R049
69120 Heidelberg

Tel.: +49 6221 54 6410
Fax: +49 6221 54 8404

Research of the Organic Device Group

The range of applications of organic materials has expanded in recent decades from purely passive to functional applications. In particular, organic pi-conjugated hydrocarbons provide solid state semiconducting properties, and thus open a wide range of potential electronic and optoelectronic devices. In this respect, organic transistors, organic photovoltaic cells and organic light-emitting diodes as technologically relevant components can be mentioned. The future will tell if other components such as sensors or memories find their way into the application. Compared to their inorganic counterparts, the benefits of the organic components are not only in manufacturing methodology holding out the prospect of a low-cost mass production, but also in the desired shape and mechanical flexibility of electronics. By this motivated, a technological progress has been achieved in recent years that has already led to the first commercial products. Despite, many fundamental physical processes occurring are not well understood in these components. This is due to the complex properties of organic semiconductors which hardly can be described by common semiconductor models. The complexity of the organic solid in turn leads to a complex behavior of organic based devices which is reinforced by the fact that other required materials such as contact materials, additional semiconductors, insulators and dopants are in use whose material properties and interactions are mostly unknown. On top, already now, a tremendous variety of organic compounds suited for functional organic devices are known and available and the sheer quantity of these compounds requires special affords in the material and device characterization.

Light-emitting organic components beyond OLEDs

One of the current research areas is related to the characterization and development of ambipolar light-emitting organic field-effect transistors (LEFETs). In particular, we participated in the development of novel devices, such as the polychromatic OLET. Up to date, the power and quantum efficiencies of the devices are strongly limiting the overall device performance and applicability. This problem must be tackled in future. In order to increase the power efficiency of the device, the LEFET architecture needs to be modified. To improve the quantum efficiency, concepts used for organic light-emitting diodes could be evaluated.

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New Materials for Organic Electronics

„By organic, one customarily means a compound containing carbon. Of the almost two million compounds known, approximately 90% are organic…“ [Electronic Processes in Organic Crystals`, Martin Pope and Charles E. Swenberg, Oxford University Press, New York, 1982] Compared to inorganic semiconducting technology, organic electronics can thus take benefit of an extraordinary variety of materials available, with an equally amount of different properties. The continuous advancement in the performance of organic semiconducting devices is thus strongly related to a steady material development at which we contribute by testing and analyzing novel materials in organic devices together with our partners in chemistry, physics and material science.

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The relation of the material properties of organic semiconductors and the overall device performance of organic functional devices is not always straight forward. Complex electrooptical material properties and contact phenomena are essential as well as the geometry and design of the device itself. To learn more about the function of the employed organic solid in an organic device we therefore simulate the device performance and experiments on basis of finite element calculations. 

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