Synthesis And Characterization Of Chalcogenide Nanomaterials For Thin Solar Cell

In recent years, Metal Chalcogenide has attracted extensive attentionand research owing to their unique physical and chemical properties.Especially the sulfide semiconductor materials (CuInS₂，CuIn_xGa_1-xS₂，Cu₂SnS₃，Cu₂ZnSnS₄) have become a hot topic in the fields of solar celldue to their excellent photoelectric and thermoelectric properties.In this paper, a mild and simple solvothermal method was used toprepare Cu₂SnS₃，Cu₂ZnSnS₄，CuInS₂nanocrystals which can used as thinsolar cell materials. And biological molecules L-cysteine was used asboth sulfur source and complex agent, it also can leads the nanoparticlesto directional growth. The as-prepared products were characterized byX-ray diffraction （XRD）, field-emission scanning electron microscopy（FESEM）, X-ray energy dispersive spectroscopy （EDS）, X-rayphotoelectron spectroscopy （XPS）, high-resolution transmission electronmicroscopy （HRTEM） and UV-Vis spectrophotometry （UV-vis）. Furthermore, the possible growth mechanisms of the products were alsoproposed. The main contents and results were summarized as follows:1. Cu₂SnS₃flowers were synthesized at180℃for16h by usingthiourea as sulfur source, glycol as solvent, the results showed that theproducts was pure phase cubic Cu₂SnS₃nanocrystals, the flowersconsisted of nanoflakes with the thickness of about20nm, and the bandgap of the products was about1.26eV which indicated the obtainedCu₂SnS₃nanocrystals applied to solar cell. The effects of copper source,solvents, temperature and time on the structure and morphology werediscussed, and the possible growth mechanism of Cu₂SnS₃flower wasalso proposed.2. Cu₂SnS₃microspheres were prepared at180℃for20h by usingL-cysteine as sulfur source, DMF as solvent. XRD spectrum showed thatthe products were pure phase cubic Cu₂SnS₃, FESEM images indicatedthat the diameter of the microsphere was about0.5-1.0μm, and plenty offlakes with the thickness of30nm on the surface of the sphere can beobserved clearly. The effects of sulfur source, solvents, temperature andtime on the structure and morphology were discussed, and the possiblegrowth mechanism of Cu₂SnS₃microsphere was also proposed.3. Kesterite Cu₂ZnSnS₄microspheres with the diameter of400-800nm were prepared at180℃for16h by using L-cysteine assulfur source, DMF as solvent. Plenty of nanoflakes with the thickness of 10-20nm on the surface of the sphere can be seen from thehigh-magnification SEM image, and the Eg value of the products is about1.48eV. XRD and FESEM were used to characterize the productsobtained by change copper source, sulfur source, solvents, temperature,time and surfactant. And the possible growth mechanism of Cu₂ZnSnS₄microsphere was also proposed.4. CuInS₂flowers with the diameter of10μm were prepared at200℃for20h by using thiourea as sulfur source, DMF as solvent. Theproducts were aggregated by nanopetals with the thickness of80nm, andthe thinner platelets can be seen on the nanopetals from thehigh-magnification SEM image. XRD and FESEM were used tocharacterize the products obtained by change sulfur source, solvents,temperature and time.5. Based on the above discussed, all reaction factors have animportant influence on the morphology of products, but have littleinfluence on structure; when ethanediamine was used as solvent, theproducts shows attempts to form Wurtzite structure, which demonstratedthat the polar of solvent plays an essential part in the phase of products;And spherical products easy to form when L-cysteine was used as sulfursource, which further explain that L-cysteine has a template function toform spherical products.