Dresden 2011 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 68: Photovoltaics: Chalcopyrites II
HL 68.10: Vortrag
Donnerstag, 17. März 2011, 12:45–13:00, FOE Anorg
Cu(In,Ga)Se2-based thin-film systems with different absorber thicknesses: spatially resolved photoluminescence and AFM measurements — •Oliver Neumann1, Stephan J. Heise1, Rudolf Brüggemann1, Max Meessen1, Wolfram Witte2, Dimitrios Hariskos2, and Gottfried H. Bauer1 — 1Institute of Physics, Carl von Ossietzky University Oldenburg, Germany — 2Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden-Württemberg (ZSW), Stuttgart, Germany
Chalcopyrite absorbers exhibit spatial inhomogeneities in structural, optical and optoelectronic properties. We study the absorber thickness dependent behavior of the local properties such as the splitting of the quasi-Fermi levels, optical threshold energies and surface roughness of Cu(In,Ga)Se2-based (CIGSe) thin-film systems with different absorber thicknesses, which are realized by etching traditionally prepared absorbers with nominal thicknesses of about 2 µm with bromine-methanol followed by a cadmium sulfide (CdS) passivation. AFM measurements reveal a decrease in the surface roughness with decreasing absorber thickness, i.e., increasing etching time. Photolumienscence experiments with high lateral resolution allow the extraction of the optical threshold energies and the splitting of the quasi-Fermi levels. Furthermore we verify a depth gradient of the gallium concentration and a variation of quasi-Fermi level splitting depending on the absorber thickness. Additionally, we show that the CdS/CIGSe junction formation of an unetched absorber in comparison to an etched absorber leads to higher quasi-Fermi level splitting.