Berlin 2012 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 72: Poster Session: Si-based Photovoltaics / Inorganic Photovoltaics / Structure and Transport in Organic Photovoltaics / Organic Semiconductors
HL 72.3: Poster
Mittwoch, 28. März 2012, 16:00–19:00, Poster D
Black Silicon solar cell emitter doping concentration measured with impedance spectroscopy — •Kay-Michael Günther1, Alexander Bomm2, Thomas Gimpel1, Stefan Kontermann2, and Wolfgang Schade1,2 — 1Clausthal University of Technology, EFZN, Am Stollen 19B, 38640 Goslar, Germany — 2Fraunhofer Heinrich Hertz Institute, Am Stollen 19B, 38640 Goslar, Germany
Exposing silicon to femtosecond-laser pulses leads to a nanostructured surface which features an enhanced light absorption. Therefore, this material is called Black Silicon. When the laser processing is performed under a sulfur-containing atmosphere, sulfur is incorporated in the silicon lattice. Secondary ion-mass spectroscopy (SIMS) shows that the silicon contains up to 0.5 at% sulfur. A pn-junction is formed for p-type base material which can be used for solar cell applications. For a solar cell solely based on Black Silicon we achieved a record efficiency of 4.5%. Nevertheless, for a device optimization the uncompensated donor concentration has to be determined. We use capacitance-voltage (C-V) measurements for obtaining the doping profiles of our samples. Because of the structured surface and the pn-junction, conventional C-V methods cannot be applied due to the interfering space charges. Therefore, we use a new method which is based on impedance spectroscopy. We can show that only a small fraction of the sulfur is electrically active and acts as a donor.