Regensburg 2013 – scientific programme
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DS: Fachverband Dünne Schichten
DS 32: Poster Session IV: Atomic layer deposition; Organic thin films; Organic Electronics and Phototovoltaics; Organic Materials for Spintronics - from spinterface to devices; Thin film photovoltaic materials and solar cells
DS 32.57: Poster
Thursday, March 14, 2013, 17:00–20:00, Poster B2
Thin magnesium silicide semiconducting films for photovoltaics — •Carina Ehrig1, 2, Ralf Krause1, Günter Schmid1, and Christoph Brabec2 — 1Siemens AG, CT RTC MAT MPV-DE, Erlangen — 2Lehrstuhl für Werkstoffe der Elektronik- und Energietechnik, FAU Erlangen-Nürnberg, Erlangen
The semiconducting magnesium silicide (Mg2Si) is a promising candidate for a low-cost and efficient absorber layer for solar cells. Its main application so far is as a high-performance thermoelectric material due to its high figure of merit. Little is known, however, about its applicability as a photoactive material. The metal-rich semiconducting Mg2Si is the only stable phase in the Mg–Si system. It has a narrow indirect band gap of 0.78 eV. Its absorption coefficient of α = 3.5 × 105 cm−1 at 2.5 eV is about 40 times higher than that of c-Si, which makes it an interesting material for producing thin solar cells.
In the present work, Mg2Si thin films were produced by thermal evaporation of Mg on Si substrates and subsequent annealing. This results in the formation of flat and homogeneous Mg2Si layers, which can be adjusted in thickness by varying the annealing temperature and time as well as the amount of Mg deposited. The Mg2Si films are characterized in terms of morphological, electrical and optical properties. Furthermore, measurements on the photoactivity of these layers will be discussed as well as several ideas for the usage of this material in solar cell devices. For example, the formation of a pn-junction consisting of a p-type silicon wafer and an n-type Mg2Si thin layer as well as other solar cell designs are proposed.