Pyrite as promising monograin layer solar cell absorber material for in-situ solar cell fabrication on the Moon

Reliable energy sources are needed in order to keep a Lunar Base on the run, and solar energy is one of the most attractive options. There are two ways to achieve it – to bring necessary solar panels from the Earth or find a way to produce them in-situ on the Moon from local resources. We propose the monograin layer (MGL) solar cell technology, that could be used for the in-situ production of solar panels on the Moon. One of the most promising compounds, that can be used as an absorber material in a monograin layer solar cell is pyrite FeS2. There are considerable amounts of iron and sulphur in the lunar regolith. Conditions for the synthesis-growth of FeS2 monograin powders were found and are presented in this study. The synthesis-growth of FeS2 powder at 740 °C in potassium iodide for one week followed by slow cooling to 575 °C and rapid cooling to the room temperature, resulted in single phase pyrite monograin powder. Powder crystals had round shape and the median size of about 50 μm was appropriate for making monograin layers. The produced FeS2 MGLs were used as absorber layers in MGL solar cells with structure as graphite/FeS2/NiO/TCO and in FeS2/Pt Schottky diodes. Charge carrier concentration of 6.2 × 1016 cm−3 was determined from capacitance-voltage measurements of FeS2/NiO heterostructure and 2.5 × 1017cm−3 from FeS2/Pt Schottky diode.