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2011
Conference Paper
Titel
One-Dimensional SiC Photonic Structures to Enhance the Efficiency of Systems with Silicon Solar Cells and Upconverters
Abstract
In silicon solar cells, photons with energies lower than the fixed bandgap of 1.12 eV are transmitted through the semiconductor material and do not contribute to current generation. This limitation can be overcome using an upconverting material below the solar cell, which transforms two or more low-energy photons into one highenergy photon, which can be utilized in the solar cell. Available efficient upconverters like NaYF4:Er, however, typically only work efficiently over a narrow wavelength range. The used spectral range can be enlarged with a second luminescent material, which absorbs over a wider spectral range and emits in the absorption range of the upconverter, a concept known as spectral concentration. In this paper, we investigate photonic structures for a special system applying both spectral and spatial concentration using fluorescent concentrators. The photonic structures ensure that all photons reach the part of the system where they can be used the most efficiently. We show that the required photonic structures can be realized with a one-dimensional stack of alternating layers of silicon carbides with different silicon to carbon ratios. We present results of the simulation and optimization of these photonic structures, as well as characterization of such structures produced in a PECVD process.