Optical spectroscopy of trap states in amorphous perylene derivative films

Emission spectra of amorphous thin films of chlorinated N,N-dimethyl-perylene-tetra-carboxylic-acid-diimide (Cl4MePTCDI) are characterized by two features: A small monomer emission and a further dominating and broad red-shifted peak. Temperature-dependent fluorescence and lifetime studies of the different excited states were carried out and led to the conclusion that the new state responsible for the red-shifted emission is populated via the excited monomeric state and vice versa. This new state can be understood as a trap caused by irregularities of the material, which can influence, for example, the twisting of the perylene core and therefore the energetics of the molecule.