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HL: Fachverband Halbleiterphysik
HL 5: Photovoltaic
HL 5.1: Vortrag
Montag, 23. März 2009, 10:15–10:30, POT 151
Spatially resolved photoluminescence measurements for a comparative analysis of CuInS2 and Cu(In,Ga)S2 thin films — •Florian Heidemann1, Levent Gütay1, Rudolf Brüggemann1, Saoussen Merdes3, Alexander Meeder2, and Gottfried H. Bauer1 — 1Institute of Physics, CvO University Oldenburg, Germany — 2SULFURCELL Solartechnik GmbH, Berlin, Germany — 3Helmholtz-Zentrum Berlin, Germany
At present chalcopyrite semiconductors like Cu(In,Ga)Se2 and Cu(In,Ga)S2 are most promising absorbers for thin film solar cells. Due to their grainy structure and inhomogeneous growth they show considerable degrees of spatial inhomogeneities in structural, optical and optoelectronic properties in the length scale of grain sizes. To analyze these locally fluctuating magnitudes we have performed spectrally resolved luminescence measurements with a high lateral resolution (≤ 1 µm) in a confocal microscope setup. This makes the determination of the spatial variation in the splitting of the quasi-Fermi levels (µ=EFn−EFp) as well as the local absorbance of the material possible. A comparison of these properties, which are crucial for the solar light conversion efficiency, is made for CuInS2 and Cu(In,Ga)S2 absorber layers for data obtained from statistically representative scan areas. The results show that an increase in bandgap and the mean µ due to an incorporation of gallium does not come along with a decrease in the variation of µ over the absorber layer. A quantification of the lateral patterns of constant µ by Minkowski-operations indicates similar pattern sizes in the range of a few µm for the analyzed samples.