Abstract Ziehlke, H. et al., 2011
Abstract: Ziehlke et al.
ABSTRACT: We characterize a series of dicyanovinyl-terthiophenes with different alkyl side chains. Variations of side chain substitution patterns and length mainly affect the morphology of the evaporated thin films, which in
turn sensitively influences properties like absorption, energy levels, and thin film roughness. To investigate hanges in transfer processes between electron donor (D) and acceptor (A) molecules due to side chain variations,
we use photoinduced absorption spectroscopy (PIA). PIA probes the longliving photoexcited species at the D_A interface: triplet excitons, cations, and anions. For a blend layer of dicyanovinyl-terthiophene and the electron
acceptor fullerene C60, an energy transfer via the singlet and triplet manifold of C60 occurs. The recombination dynamics of the triplet excitons reveal two components that differ in their lifetime and generation rate by 1 order of magnitude. By comparing the dynamics of triplet excitons in neat and blend layers, we estimate the energy transfer efficiency in dependence of the type of side chain. The compound with methyl side chains shows remarkable properties regarding thin film absorption, surface roughness, and energy transfer efficiency, which we attribute to the specific nanomorphology of the thin film.