Abstract
The antimony-iron sulfide system in general does not produce alloys below 540 °C from traditional solid-state methods. However, single source precursors have been known to produce unexpected products that arise from kinetically trapped polymorphs. In this paper, we test the efficacy of this approach toward the Fe-Sb-S system. Antimony and iron diethyldithiocarbamate complexes of the form Sb[S2CN(Et2)]3 (1) and Fe[S2CN(Et2)]3 (2) were synthesised, characterised, and used as single-source precursors for the preparation of Sb2S3, FexSy, and mixed iron antimony sulfide Sb2(1−x)Fe2xS3 (0 ≥ x ≥ 1) powders using the solvent-less thermolysis method at different temperatures ranging from 300 to 475 °C. The effect of different mole fractions of the iron precursor was evaluated on morphology, shape, and optical and magnetic properties of Sb2(1−x)Fe2xS3 (0 ≥ x ≥ 1). The obtained powders were characterized by X-ray diffraction (XRD), Raman spectroscopy scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, magnetometer measurement, and UV/vis/NIR spectroscopy. The results demonstrated that the crystalline structure, morphology, and elemental composition of the samples changed with the mole fraction of the precursor. There was significant phase separation between Sb and Fe sulfides noted from EDX spectroscopic mapping, yet an optoelectronic study monitoring the direct band gap energy of antimony sulfide shows that the band gap energy increases as a function of Fe content, which suggests limited alloying is possible from the single source route.
Highlights
The weight loss percentage for complex (2) was 17%, which is in good agreement with the calculated value of 17.5%
This indicates, as expected, some degree of phase separation as per the phase diagram, and some evidence that the approach is successful in doping in some iron into the antimony sulfide structure
The atomic percentages of antimony, iron, and sulfur at x = 0.2 were measured and all the atomic ratio of Fe to S was 45:55, which is close to the expected stoichiometry of iron sulfide determined from the X-ray diffraction (XRD) of Fe1.05 S0.95
Summary
Low dimensional absorber systems have attracted great attention because of their simple and earth abundant composition and improved performance; for example, quasi-1D antimony-based chalcogenide solar cells are nontoxic, stable, and have achieved respectable power-conversion efficiencies (PCEs) of 7–10% [16]. SSP-based synthesis methods are the preferred choice over multi-component source methods for the preparation of binary, ternary, and quaternary metal chalcogenide and thin films [30]. This method is potentially beneficial over others because of its simplicity, high purity, and ability to yield high-quality materials with better control over composition [31,32].
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