A2 (Seidel)

Zusammenfassung:

Electronically excited singlet states of organic fluorophores are typically short-lived (~ 1-10 ns). Considering practical applications, the design and characterization of chromophores with thermally activated delayed fluorescence (TADF) due to reverse intersystem crossing (rISC) from the T1 state represents an active area of recent research in organic electronics. In close collaboration with the group of Prof. Müller (A1), which will synthesize conformationally constrained fluorophores with delayed fluorescence in the range of micro- to milliseconds, we will characterize these fluorophores in this project. We will test the suitability of these fluorophores and the influence of substituents with respect to brightness, saturation behavior, dark states, photostability and for bioanalytical applications. The determination of the quantum yields of prompt and delayed fluorescence and the analysis of the corresponding fluorescence decays as a function of the environmental parameters such as solvent polarity, temperature and oxygen concentration are the important indicators to identify promising chromophores with TADF. Spectroscopy techniques will include time correlated single photon counting (TCSPC) to monitor the S1 state and coupled states via time-resolved fluorescence and transient absorption spectroscopy (TRABS), fluorescence correlation spectroscopy (FCS), and transient state (TRAST) image spectroscopy to monitor long lived non-fluorescing states such as triplet, radical or radical ion species causing the signal saturation depicted below.