Preparation And Characterization Of Semiconducter Composite SnS/SnO₂ Nanoparticles

In solar cells materials areas, improving photoelectricity conversion efficiency by compounding two kinds of semiconductor materials with similar energy band structure by nano technology is the most concerned topic. SnS has many good traits to be used as the solar cells absorption layer materials, such as innocuity, no pollution, and good matching with the natural light in spectrum, and SnO₂ is good materials for electrode materials. By compounding, SnS used as the absorption layer, and SnO₂ as electrode materials and the center of electric charge transfer; and the new materials can reduce the possibility of cavity and electron combination, increase photocurrent and photoelectricity conversion efficiency.This paper describes the details of using stannous chloride hydrate, sodium sulphide hydrate, tin chloride, urea, thiourea, ammonia and sodium hydroxide as stuffs, adopting the liquid phase method to synthesize SnS, SnO₂ and composite SnS/SnO₂ nanopowders. During the process, adopting the magnetic stir-assisted precipitation and ultrasonic-assisted precipitation method to synthesize SnS nanopowders, the precipitation and homogeneous precipitation method to generate SnO₂ nanopowders, and using mechanochemical reaction and heterogeneous nucleation method to synthesize composite SnS/SnO₂ nanopowders. Moreover, in this paper the influence ofultrasonic on the forming of polycrystalline SnS nanopowders was briefly discussed. This paper also gives the optimized process parameter of the different methods.The crystallization, morphology, size and structure features of all kinds of specimen particles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and scan electron mircroscopy (SEM). The results indicate that ultrasonic-assisted precipitation method synthesize SnS polycrystalline powders with orthorhombic structure unit and powders grain size is about 20nm. the size of SnS powders formed by the method is as much as the corresponding powders formed by the magnetic stir-assisted precipitation, but the former have good crystallization. The precipitation and homogeneous precipitation method can synthesize SnO₂ nanopowders with rutile structure unit and without non-stable orthorhombic structrue. But the crystallization of SnO₂ nanopowders formed by homogeneous precipitation method is better than the precipitation method.It can generate composite SnS/SnO₂ nanopowders with SnO₂-coated structure by using heterogeneous nucleation method, its size is about 70⁸0nm. XRD results imply the diffraction peak of SnS and SnO₂ shift which is resulted from crystal lattice aberrance, compared with the above method , there are SnO₂-coated structure but no size uniformity in the powders formed by mechanochemical reaction method. But the powders which was formed by two methods have obvious agglomeration.