Abstract
The recent development of wafer bonded four-junction concentrator solar cells (FJSCs) with record efficiency among all the existent photovoltaic (PV) cells offers new possibilities for improving the High Concentrator PV (HCPV) technology. However, the concentrator optical systems utilized in HCPV modules may have to be adapted to the new requirements of FJSC in order to properly take advantage of the increased number of p-n junctions. This research theoretically compares two identical optical concentrator systems, a Frensel lens plus a kind of refractive SILO (SIngle-Lens-Optical element) secondary (both made of PMMA, poly(methyl methacrylate)), which are equipped with a typical triple-junction concentrator solar cell (TJSC) in the one case, and with an FJSC in the other case. Both HCPV units are analyzed through ray tracing optical simulations applying an exhaustive optical modelling that takes into account the spectral responses of the different subcells within the multi-junction cells. The HCPV unit with the FJSC and PMMA SOE (secondary optical element) shows much less efficiency than that with the TJSC due to the light absorption through the PMMA SOE in the wavelength range of the bottom subcell. Therefore, PMMA SOEs may be not appropriate for FJSC in general.
Highlights
The High Concentrator PV (HCPV) (High Concentrator Photovoltaics) technology, with concentrations higher than300 times, is developed on the aim of reducing the utilization of semiconductor material at the expense of replacing it by conventional concentrator optical materials [1]
Those values are, by far, greater than those of any other PV technology [5]. Those two records utilized four-junction concentrator solar cells (FJSCs). These kinds of solar cells suppose an improvement in the development of high-efficiency concentrator multi-junction solar cells (MJSCs), since they are more efficient than the typical triple-junction concentrator solar cells (TJSCs) that are commercially available
Some of these works take into account the subcells structure of an MJSC in the optical simulations [9,10], none of these works applies an exhaustive optical modelling to an HCPV unit equipped with FJSCs
Summary
The HCPV (High Concentrator Photovoltaics) technology, with concentrations higher than. Concerning the theoretical analysis of Fresnel-based HCPV concentrator systems equipped with refractive secondary optical elements (SOEs) in the literature, many of them analyze the SILO (SIngle-Lens-Optical element) SOE [6,7,8] Some of these works take into account the subcells structure of an MJSC in the optical simulations [9,10], none of these works applies an exhaustive optical modelling to an HCPV unit equipped with FJSCs. it is needed to study how these new concentrator solar cell technology couples with typical high concentrator optical systems, as, in this case, with the combination of a Fresnel lens with the well-known SILO SOE. It is needed to study how these new concentrator solar cell technology couples with typical high concentrator optical systems, as, in this case, with the combination of a Fresnel lens with the well-known SILO SOE This new analysis will provide knowledge about if it is necessary to adapt the concentrator optics to the FJSC in order to properly take advantage of the increased number of p-n junctions. The TJSC corresponds to a commercial model [16], whereas the FJSC corresponds to that developed by Dimroth et al (wafer bonded) [17]
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