The promise of solution-processed Fe2GeS4 thin films in iron chalcogenide photovoltaics

The olivine Fe2GeS4, featuring non-toxic elements, cost-effective synthesis, and
suitable optoelectronic properties, recently emerged as a promising light-absorbing
candidate. Fe2GeS4 precursor powders obtained via a simple solutionbased
process were converted to highly crystalline Fe2GeS4 powders upon a
thermal treatment in controlled atmosphere. Thin films fabricated by dip coating
in the Fe2GeS4 precursor dispersion and subjected to the same thermal
treatment render high-purity Fe2GeS4 thin films with a band gap of 1.4 eV,
measured by room-temperature photoluminescence. Using Fe2GeS4 thin films as
the sole absorber in a solution-based solar cell, open-circuit voltages of 361 mV
are observed, while the use of the Fe2GeS4 films as counter electrodes in dyesensitized
solar cell constructs enhances the overall power conversion efficiency
of the cell by a factor of five. This is the first report of a photovoltaic device
based on Fe2GeS4.