PROCEEDINGS ARTICLE | August 1, 1990
Proc. SPIE. 1272, Optical Materials Technology for Energy Efficiency and Solar Energy Conversion IX
KEYWORDS: Semiconductors, Oxides, Thin films, Iron, Solar energy, Solar cells, Thin film solar cells, Metalorganic chemical vapor deposition, Pyrite, Absorption
Pyrite (Fe52) has been investigated as a promising new absorber material for thin film solar cell
applications because of its high optical absorption coefficient of 1OL cm1, and its bandgap of 0.9 to 1.0 eV. Thin
layers have been prepared by Metal Organic Chemical Vapor Deposition, MOCVD, Chemical Spray Pyrolysis, CSP,
Chemical Vapor Transport, CVT, and Sulfurization of Iron Oxide films, 510. It is postulated that for the material
FeS2, if x is not zero, a high point defect concentration results from replacing 2 dipoles by single S atoms. This
causes the observed photovoltages and solar conversion efficiencies to be lower than expected. Using the Fe-O-S
ternary phase diagram and the related activity plots, a thermodynamic understanding is formulated for the resulting
composition of each of these types of films. It is found that by operating in the oxide portion of the phase diagram,
the resulting oxidation state favors pyrite formation over FeS. By proper orientation of the grains relative to the
film surface, and by control of pinholes and stoichiometry, an efficient thin film photovolatic solar cell material
could be achieved.
