A new solvothermal approach to obtain nanoparticles in the Cu 3 SnS 4 -Cu 2 FeSnS 4 join

[摘要] In the field of the renewables, a large effort has been devoted in the last years to obtain conventional and new materialsfor solar energy conversion by using methods which couple a good efficiency and scalability with energetic and environmental concerns. This research has included the so-called kesterites, materials considered interesting for the thin-filmsolar cell technology, consisting of relatively abundant and harmless elements: Cu3–x–yFexZnySn(S,Se)4.In this study, we undertook the synthesis of members of the kuramite–stannite (Cu3SnS4–Cu2FeSnS4) join by means ofa two-step solvothermal approach, able to provide nanocrystalline products in an easy, low-temperature, and fast way.The sample with the highest Fe concentration was characterised by means of a multi-analytical approach, aimed to assessnot only its final structural, chemical and micromorphological features, but also the redox speciation of the two transitionmetal cations, i.e. Cu and Fe, in relation to the overall charge balance. Namely, Electron Paramagnetic Resonance (EPR),Mössbauer and X-ray Absorption Spectroscopy (XAS) and SQUID magnetometry were involved.The main results point out an excellent control of the structural features, and an intermediate Fe content in the sample,leading to the following formula unit: Cu2.2Fe0.48Sn1.2S4. The overall findings of the multi-analytical characterizationimply a complex redox balance, where inferring the site occupancy is not trivial; the charge balance, in fact, can onlybe achieved taking into account the presence of both Fe(III) and vacancies. Moreover, Fe is distributed over two different crystallographic sites.

[学科分类] 自动化工程

[关键词] p-type semiconductors;stannite;solvothermal synthesis;crystal chemistry;spectroscopy;magnetism