Regensburg 2010 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 4: Photovoltaics I: mainly CIGS
HL 4.6: Talk
Monday, March 22, 2010, 11:45–12:00, H15
Influence of sodium on the electrical properties of flexible CIGSe solar cells — •Felix Daume1,2, Stefan Puttnins1,2, Hendrik Zachmann1, Andreas Rahm1, and Marius Grundmann2 — 1Solarion AG, Ostende 5, 04288 Leipzig, Germany — 2Institut für Experimentelle Physik II, Universität Leipzig, Linnéstraße 5, 04103 Leipzig, Germany
Thin film solar cells based on Cu(In,Ga)Se2 (CIGSe) absorbers can be deposited on flexible substrates such as metal or plastic foils hence making new innovative applications and a fabrication in continuous roll-to-roll production lines feasible. Efficiencies up to 15.6 % were demonstrated for CIGSe cells on polyimide foil. The extrinsic incorporation of sodium into CIGSe solar cells based on sodium free substrates such as polyimide is indispensable to achieve high efficiencies. Despite its significance there is no comprehensive understanding of how sodium exactly influences the electrical and structural properties of CIGSe yet.
Via capacitance spectroscopy and I-V-measurement we characterized CIGSe solar cells on polyimide from a roll-to-roll fabrication with different amounts of sodium introduced during the CIGSe deposition. The net doping profiles were derived from C-V-measurements. An increase of the net doping with higher sodium content in the CIGSe is observed along with the decrease of the width of the space charge region. Additionally, differences in the spatial distribution of the doping for those CIGSe absorbers were found. These observations from capacitance spectroscopy are supplemented by I-V data showing an increase in VOC and thus in efficiency with increasing sodium content.