Synthesis of Tin (II) Sulfide nanostructures by using colloidal synthesis technique and the properties for solar cell application

• Main Authors: Betty Yan JinLiang, 龍妍妗
• Other Authors: Jow-Lay Huang
• Format: Others
• Language: en_US
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/08778658672314458724

碩士 === 國立成功大學 === 材料科學及工程學系碩博士班 === 101 === In this thesis, various sizes of tin sulfide (SnS) nanocrystalline powders under different reaction temperature and volume of the oleic acid (OA) solvent was synthesized. These nanocrystalline powders were synthesized using a tin-oleate complexes precursor, Sn(OA)x prepared by tin oxide (SnO) with different moles of oleic acid and mixture of sulfur and oleylamine (OLA) were injected into the solution of tin-oleate complexes precursor, Sn(OA)x mentioned above at different temperatures under argon atmosphere using colloidal synthesis technique. Next, the SnS powders were coated on ITO (Indium Tin Oxide) glass to form SnS films by spin coater and subsequently the properties for solar cell applications were investigated. Finally, the microstructure, optical and electrical properties of the as-prepared SnS nanocrystalline powders and films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), photoluminescence measurement, raman spectroscopy, UV-visible spectroscopy, four points probe and two points probe measurement. The analysis results showed that the SnS nanocrystalline powders were orthorhombic crystal structure, and the average particle sizes were increased from 30 nm to 50 nm, 1.5 μm, 2 μm and 1μm with increased in temperature from 150 °C to 180 °C, 210 °C, 250 °C and 310 °C, respectively. Also, changed of tetragonal SnO crystals to orthorhombic SnS nanocrystals were observed as the volume of OA solvent increased. Careful observations indicated a gradual change in the shape of these nanocrystals from spherical to sheet-like structure and finally to square sheet-like structure with the increased of the reaction temperature (150 °C – 310 °C). Photoluminescence measurement showed that SnS films displayed two strong emission bands centered at 471 nm (blue emission) and at 413 nm (UV emission), respectively and a weak emission bands existed at 454 nm (blue emission) with excitation wavelength of 230 nm. On the other hand, all the SnS films owned the Ag mode of SnS at the band around 162 and 225 cm-1 and a weak peak at 303, 304, 306 and 310 cm-1, which corresponded to the raman reference spectrum of Sn2S3 as observed in Raman spectroscopy. Besides, the optical properties of SnS films found that there was a strong absorption in the wavelength of about 1000 nm. The onset absorption for all the SnS films were in the range of 979 nm to 1014 nm and the absorption range covered the whole spectrum of ultraviolet, visible and infrared spectra, making SnS potentially better absorber materials than the commonly used CdSe nanoparticles. Additionally, the direct optical band gap is estimated to be 1.22 eV for 180 °C SnS films, 1.25 eV for 210 °C SnS films, 1.24 eV for 250 °C SnS films and 1.23 eV for 310 °C SnS films, respectively, while the indirect band gap of the SnS films is 1.06 eV for 180 °C films, 1.13 eV for 210 °C SnS films and 1.12 eV for both 250 and 310 °C SnS films, respectively. Lastly, the resistivity of the single crystalline SnS nanosheet (0.217 Ω·cm) was found to be lower than that of SnS films (103 – 108 Ω·cm). The result proved that single crystalline SnS nanosheet has good electrical property and is potentially to be applied in solar cells.