Berlin 2015 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 54: Focus Session: Nanophotonic concepts and materials for energy harvesting - Plasmonics, transformation optics, upconversion, and beyond II
HL 54.3: Vortrag
Mittwoch, 18. März 2015, 16:00–16:15, EW 201
Enhancing Upconversion with a Bragg Structure — •Clarissa Hofmann, Barbara Herter, Stefan Fischer, and Jan Christoph Goldschmidt — Fraunhofer Institute for Solar Energy Systems, Heidenhofstraße 2, 79110 Freiburg, Germany, Phone: +49 (0) 761 4588-5922 Fax: + 49 (0) 761 4588-9250
Abstract intented for focused session on Nanophotonic Concepts and Materials for Energy Harvesting - Plasmonics, Transformation Optics, Upconversion, and Beyond
Upconversion describes the generation of one higher energy photon out of at least two lower energy photons. This upconversion process can be influenced by the environment of a photonic crystal, by a modulated local density of photon states (LDOS) and an enhanced local irradiance. We present the theoretical analysis of the photonic effects of a Bragg structure on the upconversion process of the embedded upconverter β-NaYF4:25%Er3+. Considering the modulated LDOS in a rate equation model of the upconversion dynamics, we show that this effect increases the maximum possible upconversion quantum yield (UCQY) from 14% to 16% for an optimised Bragg stack design. Furthermore, due to a high irradiance enhancement, it is possible to find a Bragg stack design for each investigated incident irradiance (100 W/m2 - 5000 W/m2) that yields the maximum possible UCQY of 16%. At 200 W/m2 this corresponds to a UCQY enhancement factor of 6, making the Bragg stack a very effective photonic structure for increasing the UCQY, especially in the low irradiance range.