Optical and Electrical Transport Evaluations of n-Type Iron Pyrite Single Crystals

[Image: see text] Iron pyrite [cubic FeS(2) (cFeS(2))] is considered as an earth-abundant and low-cost thin-film photovoltaic material. However, the conversion efficiency of cFeS(2)-based solar cells remains below 3%. To elucidate this limitation, we evaluate the optical and electrical characteristics of cFeS(2) single crystals that are grown using the flux method, thus providing us an understanding of the electron transport behavior of cFeS(2) single crystals. The oxide layer on the surface of cFeS(2), which can possibly have an influence on the electrical characteristics of cFeS(2), is removed prior to characterization via optical spectroscopy and electrical transport measurement. The optical property of cFeS(2) was found to have both indirect and direct transitions. We also observed the presence of a band tail below the conduction band. The obtained electrical transport behavior indicates that cFeS(2) bulk exhibits a high defect density and a disordered phase, thus leading to the hopping conduction mechanism. Our results will pave the way for the development of photovoltaic applications with iron pyrite.