Unexpected Emissions in the Delayed Fluorescence Detection within the Porphyrin/Perylene System

Landgraf, S. (Speaker), Grampp, G. (Contributor), Alexander Wankmüller (Contributor)

Activity: Talk or presentationPoster presentationScience to science


Since the late 70s, delayed fluorescence (DF) is a well-known phenomenon in photochemis-try. It has been proved that an external magnetic field has an influence on the delayed fluores-cence yield. Most of the magnetic field effect (MFE)-studies have been undertaken in solid state systems, whereas investigations in solutions are rare. We used an energy-transfer (ET) sensitized fluorescence reaction to study the MFE of a P-type delayed fluorescence system. During our time-resolved laser spectroscopic measurements on the magnetic field effect (MFE) of delayed fluorescence within the metal-porphyrin (TPP)/perylene system in solution we found an interesting phenomena not reported in the literature up to now [1]. A narrow pre-peak arises at the beginning of the time-resolved delayed fluorescence intensity measurements.
Detailed investigations with regard to these pre-peaks rule out their origin coming from stray-light or being an artefact. It was found that the pre-peak intensities depend strongly on the solvent viscosity η. To exclude an influence of other solvent parameters, we checked two totally different solvents with similar viscosities, octanol was used additionally as a polar hydrogen-bond forming solvent. Based on energetic considerations it is assumed that pre-peaks arise from a triplet-triplet annihilation (TTA) reac-tion of the ZnTTP itself. Since the S2-state of ZnTPP is twice the energy of the T1-state such a self triplet-triplet annihilation produces a S2-state together with a So-state, see Fig. 1. From the excited S2-state decay to the S1-state occurs and finally back the So-ground state. Such a behav-iour is also observed with SnTPP having similar energy levels, but not with PdTPP where the energy conditions for forming the S2-state are not fulfilled.
[1] A. Wankmüller, Disseration Graz University of Technology (2016)
Period10 Feb 2020 - 12 Feb 2020
Held atCECP 2020 - Central European Conference on Photochemistry
Event typeConference
LocationBad Hofgastein, Austria
Degree of RecognitionInternational


  • Advanced Materials Science