Berlin 2012 – scientific programme
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O: Fachverband Oberflächenphysik
O 34: Poster Session I (Graphene; Plasmonics and nanooptics; Coherence and coherent control in nanophotonics and plasmonics)
O 34.57: Poster
Tuesday, March 27, 2012, 18:15–21:45, Poster E
Calculation of enhanced up-conversion intensity from Er3+ ions near gold nanospheres — •Florian Hallermann1, Stefan Fischer2, Deepu Kumar1, Alexander Sprafke1, Jan Christoph Goldschmidt2, and Gero von Plessen1 — 1Institute of Physics (1A), RWTH Aachen University, 52056 Aachen, Germany — 2Fraunhofer ISE, Heidenhofstr. 2, 79110 Freiburg, Germany
In conventional silicon solar cells, photons with energies below the silicon band gap (1.12 eV) do not contribute to current generation. The near-infrared part of the solar spectrum could be exploited by using up-conversion processes, such as the excitation of electrons via sequential absorption of infrared photons in suitable rare-earth ions. The electrons subsequently relax from the final state by emitting photons whose energy is high enough to be absorbed in the silicon. Here, we show on the basis of model calculations by how much the up-conversion intensity from Er3+ ions can be enhanced using spherical gold nanoparticles. In the vicinity of the nanoparticles, the excitation rate of the ions is changed due to the near-field of the particles. In addition, the relaxation times of all involved excited states of the ions are changed by the presence of metal nanoparticles due to energy transfer from the ions to the nanoparticles, which offer additional radiative and nonradiative decay channels. We calculate the effects that these changes have on the up-conversion intensity by using Mie theory combined with a rate equation system. We find a 17% enhancement for the most prominent up-conversion line emitted by Er3+ ions that are distributed over a volume around a 200 nm particle.