The Motzkus group runs and scientifically leads the fs-laser lab at the CAM. The current main focus of our work is the investigation of ultrafast dynamics of Singlet Fission (SF). Under favorable conditions, SF converts a pair of molecules residing in the ground and in the first-excited singlet states (S0S1) into a pair of triplet states (T1T1). This results in the formation of two charge carriers by absorption of a single photon and is thereby able to substantially increase the yield of organic photovoltaic devices. Since SF is globally a spin-allowed process, it occurs on an ultrafast time scale, typically fs-ps. Therefore, rapid formation of the S0S1 contact pair and fast diffusion of the long-living triplets (T1T1), preventing their annihilation, are essential for practical applications. We design under the guidance of quantum chemical calculations (Prof. A. Dreuw) and in active cooperation with other research groups (Prof. U. Bunz and Prof. L. Gade) molecular systems with the proper energy levels and analyze the SF process by means of Femtosecond Time Resolved Spectroscopy. The comparison of the photophysical behavior in spin-coated microcrystalline films and in liquid solutions of various concentrations helps to determine the characteristic time scale of SF and isolate it from pair formation and diffusion stages. Studies on covalently-bound dimers have disclosed how triplet annihilation routes can be tailored by geometrical constrains.