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Electron-exchange assisted photon energy up-conversion in thin films of ¿-conjugated polymeric composites



Panagiotis Keivanidis, Frederic Laquai, Joseph W. Robertson, Baluschev Stanislav, Josemon Jacob, Klaus Mullen, Gerhard Wegner


The mechanism of triplet-triplet annihilation (TTA) induced up-converted delayed luminescence is studied in two different binary organic systems consisting of platinum(II) octaethyl porphyrin mixed with either poly(fluorene) (PF26) or ladder-type pentaphenylene (L5Ph). Cyclic voltammetry and differential pulse voltammetry are employed for determining the ionization potentials of PtOEP, PF26 and L5Ph. Delayed luminescence spectroscopy in the μs time range suggests that the energy of the lowest excited triplet state of L5Ph is 0.20 eV higher than the triplet state of PtOEP (1.90 eV). Time-integrated photoluminescence studies confirm that the efficiency of the up-converted luminescence of L5Ph:PtOEP solutions in toluene is much more efficient than the up-converted luminescence of PF26:PtOEP. In the solid state, the phosphorescence lifetime of PtOEP in L5Ph:PtOEP 3 wt% films is lower than in the film of PF26:PtOEP 3 wt%. In contrast to the case of the PF26:PtOEP system, the up-converted luminescence of L5Ph:PtOEP blend is strongly quenched by an external electric-field. Our results suggest the participation of a charge-transfer intermediate state in the excited state pathway that leads to the generation of TTA-driven delayed up-converted luminescence in the studied composites, via TTA within PtOEP domains.
Journal of Physical Chemistry Letters


triplet-triplet annihilation, delayed fluorescence, up-conversion, organic photovoltaics, electron-exchange energy transfer


Keivanidis, P. , Laquai, F. , Robertson, J. , Stanislav, B. , Jacob, J. , Mullen, K. and Wegner, G. (2011), Electron-exchange assisted photon energy up-conversion in thin films of ¿-conjugated polymeric composites, Journal of Physical Chemistry Letters, [online], (Accessed February 28, 2024)
Created August 3, 2011, Updated October 12, 2021