Regensburg 2013 – scientific programme
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O: Fachverband Oberflächenphysik
O 84: Photovoltaics (jointly with CPP, DS and HL)
O 84.4: Talk
Friday, March 15, 2013, 10:00–10:15, H2
Admittance spectroscopy on Cu(In,Ga)Se2 solar cells with respect to sodium content — •Felix Daume1,2, Andreas Rahm1, and Marius Grundmann2 — 1Solarion AG, Ostende 5, 04288 Leipzig, Germany — 2Institut für Experimentelle Physik II, Universität Leipzig, Linnéstraße 5, 04103 Leipzig, Germany
Solar cells based on Cu(In,Ga)Se2 (CIGSe) absorbers deposited on flexible polyimide substrate enable cheap manufacturing with roll-to-roll equipment and the application in new environments such as low-load rooftops. Among present thin film flexible solar cell technologies, CIGSe achieves the highest efficiencies. The proper incorporation of sodium into the CIGSe absorber is indispensable to achieve these high efficiencies. In this study, sodium fluoride is co-evaporated during CIGSe deposition.
CIGSe solar cells with different sodium contents were investigated by admittance spectroscopy. We calculated activation energies for the N1 signature which, in literature, is widely attributed to defects. Overall concentrations and density profiles across the band gap were derived for this signature. Additionally, we derived the net doping of the CIGSe absorbers from capacitance-voltage measurements. A model based on defects at the CdS(n-type)/CIGSe(p-type) interface is proposed to explain our observations with respect to the sodium content.