Highly crystalline Fe2GeS4 nanocrystals: green synthesis and their structural and optical characterizationElectronic supplementary information (ESI) available: SEM images of the powders as a function of the milling time, EDS analysis of as-synthesized nanoparticles, and TEM images and SAED patterns of as-synthesized and heat-treated Fe2GeS4 NCs. See DOI: 10.1039/c4ta05850j

• Main Authors: Park, Bo-In, Yu, Seunggun, Hwang, Yoonjung, Cho, So-Hye, Lee, Jae-Seung, Park, Cheolmin, Lee, Doh-Kwon, Lee, Seung Yong
• Format: Journal Article
• Language: English
• Published: 20.01.2015
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c4ta05850j

The olivine Fe 2 GeS 4 compound has attracted much attention as a thermodynamically stable derivative of pyrite FeS 2 , which has been studied extensively as an earth-abundant light-absorbing candidate material. Nevertheless, reports on nanocrystalline Fe 2 GeS 4 and its optoelectronic properties are limited. Herein, Fe 2 GeS 4 nanocrystals are synthesized via a solvent-free mechanochemical process. This process not only reduces the synthesis time, but also avoids the use of hazardous solvents, thereby mitigating environmental concerns. The crystallinity of the synthesized nanocrystals is significantly enhanced by a post-heat treatment in a sulfur-containing atmosphere, showing no phase decomposition. Lattice-resolved micrographs reveal that the post-annealed nanocrystals have a hexagonal-faceted platelet structure with (002) base planes. The oxide layer near the surface region is removed by the post-annealing process, most likely due to the replacement of oxygen with sulfur in the controlled atmosphere. The post-annealed Fe 2 GeS 4 nanocrystals clearly exhibit an optical band gap of 1.43 eV and near-band-edge photoluminescent emission at 1.41 eV. This is the first experimental demonstration of the Fe 2 GeS 4 nanocrystals having optoelectronic properties that are suitable for solar applications. Highly crystalline Fe 2 GeS 4 nanocrystals were synthesized via a facile, solvent-free mechanochemical process. The post-annealed Fe 2 GeS 4 nanocrystals showed an absorption edge at 1.43 eV and a PL emission at 1.41 eV.