Solar Cells Fabricated From Minimally Processed Hematite Sources Similar to Those on the Martian Surface

Electric power produced from minimally processed in situ extraterrestrial resources may be needed to achieve extended-duration space exploration mission goals. To support this long-term goal, the photoelectrochemically active light-absorbing electrode of a solar cell was fabricated from three sources of iron-containing minerals that are expected to be similar to those found in the Martian regolith: gray hematite, oolitic hematite, and spherule hematite. The solar cells were fabricated by electrophoretic deposition or drop casting of hematite nano/microparticles onto a fluorine-doped tin oxide substrate. The photovoltaic properties of the samples were tested with a 0.5 M NaI and 0.05 M I2 redox mediator, a 0.1 M tetrabutylammonium hexafluorophosphate supporting electrolyte, an acetonitrile solvent, and a platinum counter electrode. Current–potential curves were obtained under 1 Sun (0.5 AMU at 100 mW/cm2) of white light illumination. Gray hematite generated the highest power output of 0.36 μW/cm2, yielding a power conversion efficiency of 0.36 × 10-3% for white light. In addition, wavelength-dependent solar cell efficiency was also characterized using incident photon conversion efficiency spectra, sample composition was characterized using X-ray spectra, and surface morphology was characterized using scanning electron microscopy.