Regensburg 2019 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 26: Materials for Energy Storage and Conversion

MM 26.11: Talk

Wednesday, April 3, 2019, 17:45–18:00, H43

A gasochromic Back Reflector for a Switchable Ultra-Thin Germanium Solar Cell — •Maximilian Götz, Maren Lengert, Norbert Osterthun, Kai Gehrke, Martin Vehse, and Carsten Agert — DLR-Institut für Vernetzte Energiesysteme e.V. Carl-von-Ossietzky-Str. 15 26129 Oldenburg

Magnesium-Palladium (Mg/Pd) layers are gasochromic materials, which undergo a reversible phase change from a metallic-reflective into a dielectric-transparent state upon hydrogen exposure.

In this contribution we present this layer stack as a switchable mirror for use in a Fabry-Pérot absorber. This is used to modify an ultra-thin amorphous Germanium solar cell into a switchable photovoltaic device. Germanium is placed between a transparent conductive oxide and the gasochromic switchable layer, which is used as a back reflector. Due to Hydrogen exposure the cavity resonance is decreased to single pass absorption and the layer stack becomes transparent.

Optical and material properties of the cavity are characterized by in-situ spectroscopy and ellipsometry during the switching process. Optical simulations are used to adjust the thicknesses and refractive indices of the resonator materials for optimized field enhancement in the Germanium absorber. The electrical properties of Mg/Pd as back-contact for solar cell applications are discussed and the diode behavior of the cell under illumination in reflective and transparent state is shown.