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InP based engineered substrates for CPV cells above 46% of efficiency

( 2016)
Guiot, Eric
;
Drouin, A.
;
Charles-Alfred, Cédric
;
Drazek, Charlotte
;
Buttet, A. de
;
Tauzin, Aurélie
;
Tibbits, Thomas
;
Beutel, Paul
;
Karcher, C.
;
Oliva, Eduard
;
Siefer, Gerald
;
Dimroth, Frank

By facilitating material recycling, Smart Cut â¢ technology enables the cost-effective use of expensive bulk material such as InP. In addition to this cost advantage, different handle substrates such as GaAs, Sapphire or Ge have been evaluated to enable new functions: receiver lift off, lower fragility, better integration. We have demonstrated the recycling of the InP wafer up to 7 times and evaluated up to 10 cycles. Using the InP-on-GaAs engineered substrate combined with direct wafer bonding, Soitec together with Fraunhofer ISE and CEA Leti have demonstrated wafer bonded 4-junction solar cells with highest conversion efficiency of 46.1 %. In parallel, equivalent solar cell performances are demonstrated either on bulk InP substrate or InP engineered substrate.
III-V multi-junction solar cell using metal wrap through contacts

( 2016)
Salvetat, Thierry
;
Oliva, Eduard
;
Tauzin, Aurélie
;
Klinger, Vera
;
Beutel, Paul
;
Jany, C.
;
Thibon, R.
;
Haumesser, P.-H.
;
Hassaine, A.
;
Mourier, T.
;
Rodriguez, G.
;
Lecouvey, Christophe
;
Imbert, Bruno
;
Fournel, Frank
;
Fabbri, J.-M.
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Moulet, J.-S.
;
Dimroth, Frank
;
Signamarcheix, Thomas

The Solar cell front side is a key design point for improved cell efficiency as a trade is made between optical losses (shadowing effect) and electrical losses (resistance). One solution consists in frontside contacts report to the cell's backside using through device conductive vias. By this way metal shadowing could be drastically reduced without increasing resistive losses. Such architecture is called Metal Wrap Through (MWT) and has been developed on silicon solar cells. Its application to III-V Multi-Junctions Solar Cells (MJSC) could be of great interest and has been simulated and studied for several years. We present here first functional MWT III-V dual-junction solar cells. Prototype developments have been based on inverted tandem solar cell (GaInP/GaAs) epitaxial structures grown on GaAs substrates. Front side contacts have been reported on the device's backside using specifically adapted Trough Semiconductor Via (TSV) technologies. Finally, the III-V active fi lm was transferred on a conductive receiver by copper to copper (Cu//Cu) direct metal bonding. Morphological and chemical characterizations showed metallized and isolated contacts going through the tandem solar cell's structure. Electrical characterizations displayed many functional cells across 100mm wafers reaching efficiencies up to 26.3% @1 sun AM1.5d spectrum with a fill factor (FF) of 87.1%. Under concentration the efficiency raised up to 28.3% @167 suns. Beside these demonstrators, developed processes open ways to various possibilities such as large area III-V MJSC receivers.
Four-junction wafer-bonded concentrator solar cells

( 2016)
Dimroth, Frank
;
Tibbits, Thomas
;
Niemeyer, Markus
;
Predan, Felix
;
Beutel, Paul
;
Karcher, Christian
;
Oliva, Eduard
;
Siefer, Gerald
;
Lackner, David
;
Fuß-Kailuweit, Peter
;
Bett, Andreas W.
;
Krause, Rainer
;
Drazek, Charlotte
;
Guiot, Eric
;
Wasselin, Jocelyne
;
Tauzin, Aurélie
;
Signamarcheix, Thomas

The highest solar cell conversion efficiencies are achieved with four-junction devices under concentrated sunlight illumination. Different cell architectures are under development, all targeting an ideal bandgap combination close to 1.9, 1.4, 1.0, and 0.7 eV. Wafer bonding is used in this work to combine materials with a significant lattice mismatch. Three cell architectures are presented using the same two top junctions of GaInP/GaAs but different infrared absorbers based on Germanium, GaSb, or GaInAs on InP. The modeled efficiency potential at 500 suns is in the range of 49-54% for all three devices, but the highest efficiency is expected for the InP-based cell. An efficiency of 46% at 508 suns was already measured by AIST in Japan for a GaInP/GaAs//GaInAsP/GaInAs solar cell and represents the highest independently confirmed efficiency today. Solar cells on Ge and GaSb are in the development phase at Fraunhofer ISE, and the first demonstration of functional devices is presented in this paper.
Four-junction wafer bonded concentrator solar cells

( 2015)
Dimroth, Frank
;
Tibbits, Thomas
;
Niemeyer, Markus
;
Predan, Felix
;
Beutel, Paul
;
Karcher, C.
;
Oliva, Eduard
;
Siefer, Gerald
;
Lackner, David
;
Fuß-Kailuweit, P.
;
Bett, Andreas W.
;
Krause, R.
;
Drazek, Charlotte
;
Guiot, Eric
;
Wasselin, Jocelyne
;
Tauzin, Aurélie
;
Signamarcheix, Thomas

The highest solar cell conversion efficiencies are achieved with Four-junction devices under concentrated sunlight illumination. Different cell architectures are under development, all targeting an ideal bandgap combination close to 1.9 eV, 1.4 eV, 1.0 eV and 0.7 eV. Wafer bonding is used in this work to combine materials with a significant lattice-mismatch. Three cell architectures are presented using the same two top junctions of GaInP/GaAs but different infrared absorbers based on Germanium, GaSb or GaInAs on InP. The modelled efficiency potential at 500 suns is in the range of 49-54 % for all three devices but the highest efficiency is expected for the InP-based cell. An efficiency of 46 % at 508-suns was already measured by AIST in Japan for a GaInP/GaAs//GaInAsP/GaInAs solar cell and represents the highest independently confirmed efficiency today. Solar cells on Ge and GaSb are in the development phase at Fraunhofer ISE and first demonstration of functional devices is presented in this paper.
InP-based composite substrates for four junction concentrator solar cells

( 2015)
Tauzin, Aurélie
;
Lagoutte, Emmanuelle
;
Salvetat, Thierry
;
Guelfucci, Jude
;
Bogumilowicz, Yann
;
Imbert, Bruno
;
Fournel, Frank
;
Reboh, Shay
;
Luce, Flavia Piegas
;
Lecouvey, Christophe
;
Chaira, Tarik
;
Carron, Véronique
;
Moriceau, Hubert
;
Duvernay, Julien
;
Signamarcheix, Thomas
;
Drazek, Charlotte
;
Charles-Alfred, Cédric
;
Ghyselen, Bruno
;
Guiot, Eric
;
Tibbits, Thomas
;
Beutel, Paul
;
Dimroth, Frank

A photovoltaics conversion efficiency of 46% at 508 suns concentration was recently demonstrated with a four-junction solar cell consisting in a GaAs-based top tandem cell transferred onto an InP-based bottom tandem cell, by means of wafer bonding. We have successfully produced and characterized different InPOS (for InP-On-Substrate) composite substrates, that could advantageously replace fragile and expensive InP bulk wafers for the growth of the bottom tandem cell. The InPOS composite substrates include a thin top InP layer with thickness below 1µm, transferred onto a host substrate using the Smart CutTM layer transfer technology. We developed InP-On-GaAs, InP-On-Ge and InP-On-Sapphire substrates with surface and crystal qualities similar to the InP bulk ones. A low electrical resistance of 1.4mΩ.cm² was measured along the InP transferred layer and the bonding interface. An epitaxial bottom tandem cell was grown on an InPOS substrate, and the corresponding PL behavior was found identical to that of cells grown on InP bulk reference. The InP-based composite substrates are then very well suited for the fabrication of advanced devices like four-junction solar cells.
Wafer bonded four-junction GaInP/GaAa/GaInAsP/GaInAs concentrator solar cells with 44.7% efficiency

( 2014)
Dimroth, Frank
;
Grave, M.
;
Beutel, Paul
;
Fiedeler, U.
;
Karcher, C.
;
Tibbits, Thomas
;
Oliva, Eduard
;
Siefer, Gerald
;
Schachtner, Michael
;
Wekkeli, Alexander
;
Bett, Andreas W.
;
Krause, R.
;
Piccin, M.
;
Drazek, Charlotte
;
Guiot, Eric
;
Ghyselen, B.
;
Salvetat, T.
;
Tauzin, Aurélie
;
Signamarcheix, Thomas
;
Dobrich, A.
;
Hannappel, Thomas
;
Schwarzburg, K.
;
Blanc, N.

Triple-junction solar cells from III-V compound semiconductors have thus far delivered the highest solar-electric conversion efficiencies. Increasing the number of junctions generally offers the potential to reach even higher efficiencies, but material quality and the choice of bandgap energies turn out to be even more importance than the number of junctions. Several four-junction solar cell architectures with optimum bandgap combination are found for lattice-mismatched III-V semiconductors as high bandgap materials predominantly possess smaller lattice constant than low bandgap materials. Direct wafer bonding offers a new opportunity to combine such mismatched materials through a permanent, electrically conductive and optically transparent interface. In this work, a GaAs-based top tandem solar cell structure was bonded to an InP-based bottom tandem cell with a difference in lattice constant of 3.7%. The result is a GaInP/GaAs//GaInAsP/GaInAs four-junction solar cell with a new record efficiency of 44.7% at 297-times concentration of the AM1.5d (ASTM G173-03) spectrum. This work demonstrates a successful pathway for reaching highest conversion efficiencies with III-V multi-junction solar cells having four and in the future even more junctions.
Development of high efficiency wafer bonded 4-junction solar cells for concentrator photovoltaic applications

( 2014)
Dimroth, Frank
;
Tibbits, Thomas
;
Beutel, Paul
;
Karcher, C.
;
Oliva, Eduard
;
Siefer, Gerald
;
Schachtner, Michael
;
Wekkeli, Alexander
;
Steiner, Marc
;
Wiesenfarth, Maike
;
Bett, Andreas W.
;
Krause, R.
;
Gerster, E.
;
Piccin, M.
;
Blanc, N.
;
Munoz Rico, M.
;
Drazek, Charlotte
;
Guiot, Eric
;
Wasselin, Jocelyne
;
Arena, C.
;
Salvetat, Thierry
;
Tauzin, Aurélie
;
Signamarcheix, Thomas
;
Hannappel, Thomas

The next generation of multi-junction concentrator solar cells will have to reach higher efficiencies than today's devices. At the same time these solar cells must be reliable in the field, be manufacturable with good yield and at sufficiently low cost. Inevitably the request of higher efficiency requires four or even more junction devices. A four-junction solar cell combination of GaInP/GaAs//GaInAsP/GaInAs with bandgap energies of 1.9, 1.4, 1.1, 0.7 eV is developed in a close collaboration between the Fraunhofer ISE, Soitec, CEA-LETI and HZB. This 4-junction cell hits close to the optimum of theoretical efficiency contour plots and has the potential to reach efficiencies up to 50 % under concentration. Challenges are associated with lattice-mismatch between GaAs and InP which is overcome by direct wafer-bonding. The high cost of the InP is addressed by the use of engineered substrates which only require a 500 nm thin mono-crystalline InP layer instead of several hundr ed m. Excellent solar cell results up to 44.7 % efficiency have been obtained under concentration for devices manufactured on InP bulk substrates. The high cell efficiency is also supported by out-door characterization of one cell below a Fresnel lens with 16 cm2 aperture area. 38.5 % conversion efficiency has been measured for this mono-module in Freiburg under real operating conditions without any corrections.
Demonstration of single crystal GaAs layers on CTE-matched substrates by the Smart Cut technology

( 2012)
Jouanneau, T.
;
Bogumilowicz, Yann
;
Gergaud, P.
;
Delaye, V.
;
Barnes, J.-P.
;
Klinger, Vera
;
Dimroth, Frank
;
Tauzin, Aurélie
;
Ghyselen, Bruno
;
Carron, Véronique

Templates made of a thin single crystal GaAs layer on CTE-matched substrate (sapphire) have been realized using the Smart Cut technology. These templates can withstand high processing temperatures thanks to the CTE matching between the GaAs thin film and its support, and therefore can be used for many applications since they require no specific restriction concerning thermal treatments. The GaAs templates have been compared to conventional bulk GaAs substrates. TEM images and XRD spectra show similar crystalline quality. AFM measurements show a similar surface microroughness. Photoluminescence of a AlGaAs double heterostructure grown by MOCVD on the GaAs template shows the same intensity as a reference structure on bulk GaAs. Therefore, the GaAs templates can replace GaAs bulk substrates in various domains such as photonics devices (solar cell, laser) or high frequency electronics. ©The Electrochemical Society.
III-V solar cell growth on wafer-bonded GaAs/Si-substrates

( 2006)
Schöne, Jan
;
Dimroth, Frank
;
Bett, Andreas W.
;
Tauzin, Aurélie
;
Jaussaud, C.
;
Roussin, J.-C.

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