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Advanced upconverter systems with spectral and geometric concentration for high upconversion efficiencies

: Goldschmidt, J.C.; Löper, P.; Fischer, S.; Janz, S.; Peters, M.; Glunz, S.W.; Willeke, G.; Lifshitz, E.; Krämer, K.; Biner, D.


Faraone, L. ; Institute of Electrical and Electronics Engineers -IEEE-:
COMMAD 2008, Conference on Optoelectronic and Microelectronic Materials and Devices. Proceedings : 28 July - 1 August 2008, Sydney, Australia; In conjunction with the IUMRS-ICEM 2008 International Conference on Electronic Materials
Piscataway/NJ: IEEE, 2008
ISBN: 978-1-4244-2717-8
ISBN: 978-1-4244-2716-1
Conference on Optoelectronic and Microelectronic Materials and Devices (COMMAD) <7, 2008, Sydney>
International Conference on Electronic Materials (ICEM) <2008, Sydney>
Fraunhofer ISE ()

In this paper we present an advanced upeonverter system concept to reduce the sub-bandgap losses of silicon solar cells. We address the issue of the narrow absorption range of common upconverter materials. This problem can be overcome by the combination of the upconverter with a broadly absorbing fluorescent material, which emits in the absorption range of the upconverter. However, possible fluorescent materials also absorb in the emission range of the upconverter. We therefore propose an advanced system setup, which avoids unwanted absorption by separating upconverter and fluorescent material with a selectively reflective photonic structure. The incorporation of the fluorescent material in a fluorescent concentrator allows for additional geometric concentration increasing the efficiency of the upconversion process. We estimate that a total system efficiency of up to 25% could be possible with an Er based upconverting system and a silicon solar cell.