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MM: Fachverband Metall- und Materialphysik

MM 26: Poster Session

MM 26.67: Poster

Dienstag, 23. März 2010, 14:45–16:30, Poster C

Minority carrier lifetime of InGaAsP and InGaAs absorbers for low bandgap tandem solar cells — •Nadine Szabó, B. Erol Sagol, Ulf Seidel, Klaus Schwarzburg, and Thomas Hannappel — Helmholtz-Zentrum Berlin für Materialien und Energie GmbH Hahn-Meitner-Platz 1 14109 Berlin

At present, III-V triple junction (3J) solar cells are achieving the highest conversion efficiencies (η=41.6%) worldwide. 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 hetero structures (DHS). This technique is both sensitive for the quality of the bulk material within the DHS as well as for the interface preparation between barrier and bulk.