Measurement system for time-resolved optical spectroscopy

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The Organic Semiconductors Group works on the understanding of elementary processes in light-emitting materials and, in particular, on the limitations concerning the efficiency of devices. One of our most important achievements in this field was the finding that many organic dyes used as light emitters in guest-host systems exhibit a non-isotropic orientation distribution of their optical transition dipole moments. These and related questions are subject of current and planned future research projects.In this context, the proposed measurement system for time-resolved optical spectroscopy will allow us to gain detailed insights into excited-state dynamics of organics as well as novel nano-scale emitter materials over a wide range in time and, specifically, with respect to reorientation of their electronic dipole moments.To this end, we need a tunable pulsed laser system with sufficiently short pulse length and enough pulse energy over a wide spectral range from the ultra-violet across the entire visible region. By combining it with an already existing streak camera system, we will be able to study luminescence dynamics of a broad range of emitter materials across a wide time window, spanning from a few hundred picoseconds to milliseconds (or longer if required).Furthermore, the planned radiation pattern analysis of the light-emitting species – and, in particular, possible reorientation of the same during the excited state lifetime – requires a spectrograph with excellent imaging quality connected to a gated intensified charge-coupled device as detector. For the investigation of emitter orientation, we can tolerate a slightly diminished time resolution in the nanosecond range; however, with the envisioned new setup for back focal plane imaging we plan to capture the relevant momentum and energy range in a single exposure. This will allow studying dynamic reorientation processes of optical excitations in complex emitter systems.The proposed new setup will strengthen the leading position of the group in the field of orientation studies of organic and nano-scale inorganic emitter materials and implement a novel method that is not available to date.