Tahirzeb Khan

• In the last 25 years, nano science has developed rapidly because of increased scientific demand and technological interest not only in material science, but also in e.g. life sciences and other related fields. The properties of bulk and nano-structured materials differ considerably; therefore the interest to investigate the fundamental properties of materials on a nanometer scale continues to grow. In our research, we focus on the investigation of elementary processes, including energy transfer, charge transport, and exciton diffusion in nano-systems, which also involve the vibrational properties of these systems and their environments. These processes occur on ultrashort time scales, and therefore require femtosecond temporal resolution as well as high spatial resolution for their investigation. However, the standard far-field diffraction-limited microscopic techniques cannot access the detailed local properties of nanostructure-based organic electronic devices made of thin films, whereas certain local details can severely hamper the performance of organic semiconductors. In order to obtain relevant information, the best if not the only solution is to apply a technique able to access high spatially localized and temporal information, and to this end, the combination of scanning near-field microscopy (SNOM) with time-resolved spectroscopy offers a superior tool, which can be used. In this thesis, we demonstrate that the combination of nanometer spatial resolution and femtosecond time resolution is feasible for model samples of novel organic semiconductors. We introduce different nonlinear spectroscopic techniques such as pump-probe transient absorption measurements as well as coherent anti-Stokes Raman scattering (CARS), combined with scanning near field optical microscopy and apply them to different organic semiconductor systems, focusing mainly on 3, 4, 9, 10-perylene tetra carboxylic dianhydride (PTCDA) and poly 3-hexylthiophene (P3HT).