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Conjugated organic molecules and polymers enable the demonstration of flexible semiconductor devices that can be processed at low temperature onto different substrates with variable form factors. Over the past decades, device performance has improved greatly as a large number of new compounds were synthesized and tested in various device geometries. While molecular-level models have been successful in providing a rational design of molecules and polymers for higher performance, models to predict the morphology of thin films and consequently macroscopic physical properties, such as charge mobility, remain elusive. The lack of such models has resulted in a trial and error approach and limits our ability to predict ultimate performance. Furthermore, organic solids exhibit photophysical properties that are unique and different from those of conventional inorganic semiconductors. The question then arises whether semiconductor equations developed for inorganic semiconductor devices can be applied to describe the physical properties of organic electronic devices. In this talk, we will highlight some fundamental differences in the physical properties between organic and inorganic semiconductors, but show that general models such as the Shockley diode equation can be applied to organic photodiodes and solar cells. In particular, we will emphasize the importance to understand and mitigate parasitic effects such as shunt resistance effects in these devices as they often overshadow the intrinsic physical properties and can lead to different interpretations of results.

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Bernard Kippelen, Georgia Institute of Technology
Seminar Room, Institute of Physics II
Contact: Klaus Meerholz