| Autor: |
Baluschev, S., Yakutkin, V., Wegner, G., Minch, B., Miteva, T., Nelles, G., Yasuda, A. |
| Předmět: |
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| Zdroj: |
Journal of Applied Physics; Oct2007, Vol. 102 Issue 7, p076103, 2p, 1 Graph |
| Abstrakt: |
We have studied the phenomenon of photon upconversion in systems of two model compounds as highly efficient blue emitters sensitized with metallated macrocycle molecules in thin films. Aggregation between the active molecules (metallated porphyrins and anthracene derivatives) indeed plays a very important role in the triplet-triplet annihilation supported photon upconversion process. Contrary to the suggestions of Steer [J. Appl. Phys. 102, 076102 (2007)] aggregation (followed from phase separation) is a highly undesired effect: external quantum yields of the level of 1%–3% are observed only in systems with a low degree of aggregation (solutions), whereas the solid state films exhibit at least order of magnitude lower upconversion quantum yield than solutions. Additionally, the “only excitons in aggregates model” cannot explain the increase of the linear absorption of the sensitizer at the presence of the emitter. Furthermore, this hypothesis cannot explain why the upconversion quantum yield increases when decreasing the total molecular concentration. Finally, the only excitons in aggregates model needs to assume equal aggregation properties of molecules with different solubilities, sizes, and decorations, as the case of PdPh4TBP and PdPh4OMe8TNP. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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