Regensburg 2013 – wissenschaftliches Programm

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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

Donnerstag, 14. März 2013, 17:00–20:00, Poster B2

Thin magnesium silicide semiconducting films for photovoltaics — •Carina Ehrig^{1, 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.