Increasing the Band Gap of Iron Pyrite by Alloying with Oxygen

摘要

Systematic density functional theory studies and model analyses have been used to show that the band gap of iron pyrite (FeS_2) can be increased from ～1.0 to 1.2-1.3 eV by replacing ～10% of the sulfur atoms with oxygen atoms (i.e., ～10% O_s impurities). O_s formation is exothermic, and the oxygen atoms tend to avoid O-O dimerization, which favors the structural stability of homogeneous FeS_(2-x)O_xc alloys and frustrates phase separation into FeS_2 and iron oxides. With an ideal band gap, absence of O_s-induced gap states, high optical absorptivity, and low electron effective mass, FeS_(2-x)O_x alloys are promising for the development of pyrite-based heterojunction solar cells that feature large photovoltages and high device efficiencies.