Regensburg 2010 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 62: Poster II: Photovoltaics and Organic Semiconductors
HL 62.28: Poster
Donnerstag, 25. März 2010, 18:00–20:00, Poster D2
Maximum voltage determined by appropriate superposition of photoluminescence from polycrystalline Cu(In,Ga)S2 absorber layers — •Florian Heidemann1, Rudolf Brüggemann1, Saoussen Merdes2, Alexander Meder3, and Gottfried H. Bauer1 — 1Institute of Physics, CvO University Oldenburg, Germany — 2SE2, Helmholtz-Zentrum Berlin, Germany — 3SULFURCELL Solartechnik GmbH, Berlin, Germany
Thin film solar cells based on the chalcopyrite Cu(In,Ga)S2 offer an alternative to the predominant Cu(In,Ga)Se2 with the benefit of higher band-gap and thus of nominal higher open circuit voltage Voc. We have performed calibrated photoluminescence (PL) studies on absorbers to characterize their optoelectronic quality. To record spectrally resolved PL with sufficient photon fluxes we collect PL signals from a homogeneously illuminated area of 1 mm2. Due to absorber polycrystallinity the collected PL-signal is composed of contributions of individual sites in the µm-scale varying in intensity and spectral shape. Since the splitting of quasi-Fermi levels (EFn − EFp) according to Planck’s generalized law is derived from the logarithm of the spectral PL yield, measuring without sufficient local resolution leads to an overestimation of EFn − EFp. With a second confocal setup we analyze spectrally resolved PL with a lateral resolution of less than 1 µm. For detection limitations we need excitation fluxes in the order of 104 AM1.5 to extrapolate from distribution functions of PL signals recorded at 300 K and high excitation towards AM1.5. We correct EFn − EFp from the calibrated setup, which corresponds to the maximum achievable Voc.