Ultrafast Processes in Organic Semiconductor Devices

Conjugated organic semiconducting materials are attracting enormous interest with regard to their application as active materials in electronic and optoelectronic devices. Displays exploiting the electroluminescence of conjugated small molecules are already available in commercial products such as car stereos, mobile phones and digital cameras. The essential advantages of these materials are the cheap and relatively simple processing since they can be easily spin-cast from solution or, for higher versatility, ink-jet printed. Moreover, optical properties like the fluorescence spectrum can easily be chemically tuned. The development of "plastic" electronic circuits is driven by field effect transistors (FET) with increasing on-off ratio and FET-LED integrated optoelectronic devices. Organic photovoltaic cells have reached a power conversion efficiency of 3 %.The physical understanding of fundamental properties has constantly backed the achievements in practical applications. At this point a rather comprehensive background for discussing the optical and electrical properties has been established, however, some critical issues are still left unclear. Time-resolved spectroscopy is a powerful tool for investigating elementary excitation dynamics and has contributed significantly to this field, in particular by enhancing the understanding of the fundamental photophysics. A variety of ultrafast phenomena in organic semiconductor materials as well as electronic and optoelectronic devices based on these will be investigated with new experimental tools, uniting vanguard laser systems delivering pulses of sub-10-fs duration and organic device technology. Among these phenomena are the generation of electrical charge carriers, the interaction of charge carriers with excited states, the electronic structure of chemical defects forming under operation, and the real-time monitoring of molecular vibrations. Materials investigated will be technologically prominent conjugated polymers, such as the poly-fluorene family. Expected achievements of the program are the development of new tools and configurations for probing organic semiconductors and the determination of new insight into photophysical phenomena of technological relevance.