Berlin 2015 – scientific programme

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DF: Fachverband Dielektrische Festkörper

DF 3: Photovoltaics: Kesterites and Less Widely used Materials (HL with DF)

DF 3.7: Talk

Monday, March 16, 2015, 12:45–13:00, ER 164

Formation of n-type defect levels in 1.0 eV GaInNAs layers and their influence on GaInNAs solar cell performance — •Fabian Langer, Svenja Perl, Sven Höfling, and Martin Kamp — Technische Physik and Wilhelm Conrad Röntgen Research Center for Complex Material Systems, University of Würzburg, Am Hubland, D97074 Würzburg, Germany

The semiconductor material GaInNAs can be grown lattice matched to GaAs/Ge by molecular beam epitaxy (MBE) with a broad degree of freedom in its bandgap. Besides emerging applications like telecommunication light sensing requiring bandgaps below 0.95 eV, GaInNAs material with a 1.0 eV wide bandgap is of increasing interest for the solar cell industry. Up to now the market for space or concentrator photovoltaic (CPV) is dominated by solar cells made of the material combination GaInP/(In)GaAs/Ge. However, this type of solar cell has reached its practical average efficiency limit. But further improvement by the integration of a 1.0 eV GaInN(Sb)As junction could already be shown. In this presentation we report on the investigation of n-type defects formed during the GaInNAs growth and analyze their influence on the performance of 1.0 eV GaInNAs solar cells. Utilizing these defects we achieved very high internal quantum efficiencies above 90 % due to a compensation effect of the background p-doping in the GaInNAs layer. However, this comes along with a strongly increased dark current generated by the defect states within the bandgap and results in reduced open-circuit voltages of about 0.2 V.