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AKE: Arbeitskreis Energie

AKE 11: Photovoltaik

AKE 11.3: Vortrag

Mittwoch, 16. März 2011, 17:15–17:30, BEY 118

GaInP/GaAs/Si Triple-Junction Solar Cell Formed by Wafer Bonding — •Karen Dreyer, Elvira Fehrenbacher, Eduard Oliva, Antonio Leimenstoll, Felix Schätzle, Martin Hermle, Andreas Bett, and Frank Dimroth — Fraunhofer-Institut für Solare Energiesysteme ISE, Freiburg

Multi-junction solar cells utilise the solar spectrum more efficiently than single-junction devices by combining several pn-junctions of different bandgap energy. A combination of GaInP (Eg = 1.9 eV), GaAs (Eg = 1.4 eV) and Si (Eg = 1.1 eV) is nearly ideal for converting the solar spectrum. The direct growth of such highly lattice mismatched semiconductors is challenging. Wafer bonding offers a way for the combination of semiconductors regardless of their lattice constant. This presentation reports on the realization of a highly lattice mismatched triple-junction solar cell. A prefabricated GaInP/GaAs dual-junction and a silicon solar cell are combined by the use of surface activated wafer bonding. In this process the surfaces of the cell structures are cleaned by a beam of argon atoms in a UHV chamber. The wafers are brought into contact immediately after the surface activation which initializes the bonding. Under a solar simulator the GaInP/GaAs/Si triple-junction solar cell had an efficiency of 20.5 % under 1-sun AM1.5 conditions and 23.1 % under the concentrated AM1.5d spectrum (concentration ratio: 48 X). Different factors like the resistance of the bond interface and the current mismatch between the subcells are still limiting the device performance and will be discussed in the presentation.