Dresden 2009 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 48: Poster 2

HL 48.82: Poster

Donnerstag, 26. März 2009, 15:00–17:30, P2

Optical and electrical characterisation of InP-based multijunction solar cells — •Nadine Szabo, Erol Sagol, Christian Höhn, Marinus Kunst, Klaus Schwarzburg, and Thomas Hannappel — Helmholtz Zentrum Berlin, Glienicker Str. 100, 14109 Berlin

Currently, triple-junction solar cells realized from III-V semiconductor compounds hold the solar energy conversion efficiency world record. To improve the efficiency significantly, it is necessary to increase the number of junctions and to involve a subcell with an absorber layer in the band gap range of 1eV. We show on the example of the low band gap tandem cell how the choice of the materials, the quality of the bulk, the optimization of the band gap energies and the preparation of the critical interfaces are essential to build a high efficiency solar cell. A four-junction device can be realized by mechanically stacking of a GaAs-based GaInP/GaAs tandem cell with a InP-based InGaAsP/InGaAs tandem cell. We have grown InGaAsP and InGaAs-layers lattice matched to InP substrates, and investigated the properties of the absorber bulk material. We will present time resolved photoluminescence measurements of low band gap InGaAs and InGaAsP double heterostructures and I-V curves of InGaAs/GaAsSb tunnel junctions. Our results show that the InGaAsP/InGaAs tandem cells reach efficiencies above 10% under GaAs, which is considerably higher than a conventional germanium subcell.