Magnesium Fluoride Electron-Selective Contacts for Crystalline Silicon Solar Cells

In this study, we present a novel application of thin magnesium fluoride films to form electron-selective contacts to n-type crystalline silicon (c-Si). This allows the demonstration of a 20.1%-efficient c-Si solar cell. The electron selective contact is composed of deposited layers of amorphous silicon (similar to 6.5 nm), magnesium fluoride nm), and aluminum (similar to 300 nm). X-ray photoelectron spectroscopy reveals a work function of 3.5 eV at the MgF2/Al interface, significantly lower than that of aluminum itself (similar to 4.2 eV), enabling an Ohmic contact between the aluminum electrode and n-type c-Si. The optimized contact structure exhibits a contact resistivity of similar to 76 m Omega cm(2), sufficiently low for a full-area contact to solar cells, together with a very low contact recombination current density of similar to 10 fA/cm(2). We demonstrate that electrodes functionalized with thin magnesium fluoride films significantly improve the performance of silicon solar tells. The novel contacts can potentially be implemented also in organic optoelectronic devices, including, photovoltaics, thin film transistors, or light emitting diodes.