Solution synthesis of single-crystalline Fe2GeS4 nanosheets

• Fe2GeS4 nanosheets are synthesized via one-pot heating up method.
• 1-docanethiol used as air-stable sulfur precursor.
• Fe2GeS4 nanosheets are single crystalline in nature.
• Nanosheets have an optical band gap of 1.38 eV, which is suitable for light absorber in solar cells.

Pyrite (FeS2) has been extensively studied as low cost light absorber in thin film photovoltaics. However, the instability of FeS2 phase limits its performance in photovoltaics. Recently, olivine Fe2GeS4 has been proposed as thermodynamically stable alternative for the unstable FeS2 phase. Despite its attractive properties, studies on this material is quite limited. This is due to the difficulties associated with the synthesis. Herein, we report a simple one-pot colloidal synthesis of Fe2GeS4 nanosheets using 1-dodecanethiol as air-stable sulfur source. We have studied the favorable reaction conditions to form phase pure Fe2GeS4 nanosheets. The nanosheets are single-crystalline in nature and have an average size of 800 nm and thickness around 64 nm. The optical band gap of Fe2GeS4 is calculated to be 1.38 eV, which is optimal for photovoltaic applications.