Dresden 2011 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 85: Poster Session II

HL 85.67: Poster

Donnerstag, 17. März 2011, 18:00–21:00, P4

Optical and Electrical Characterization of InP-based Low Bandgap Multijunction Solar Cells — •Anja Dobrich, Nadine Szabó, Klaus Schwarzburg, and Thomas Hannappel — Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, 14109 Berlin, Germany

At present, III-V triple junction (3J) solar cells are achieving the highest conversion efficiencies (η=41.6%) worldwide. The current record multi junction solar cell grown on germanium, having Ge, Ga(In)As and GaInP as subcells, but still considerably higher efficiencies can be achieved with a four junction (4J) configuration, which has optimized band gaps around 1.9, 1.4, 1.0 and 0.7 eV. This can be realized with a mechanically stacked GaAs-based GaInP/GaAs tandem and an InP based InGaAsP/InGaAs tandem cell. For this purpose, we have grown InGaAsP/InGaAs tandem solar cells lattice-matched to InP by MOVPE.

The lifetime of minority charge carriers affects strongly the performance of solar cells, hence it is one of the most important properties of photovoltaic absorbers. Results of minority carrier lifetime measurements for the IR-bandgap compounds InGaAsP (1.03 eV) / InGaAs (0.73 eV) are presented. This technique is sensitive for both, the quality of the bulk material within the double hetero structure (DHS) as well as the interface preparation between barrier and bulk. Furthermore, by scanning the sample, spatial inhomogeneities in the lifetime can be detected. We show the effect of different interface preparation routines on the minority charge carrier lifetime.