| Chalcopyrite semiconductors represent one of the most important types of nanomaterial. In the past fewyears, the syntheses, physical properties of chalcopyrite semiconductor nanocrystals, and their applicationin various fields have received in depth investigations. Cu2ZnSnS4(CZTS) is a quaternary semiconductormaterial which are formed by replacing two In(III) ion with Zn(II) and Sn(IV).Synthetic methods for the CZTS materials can be classified into two main categories: vacuum-basedmethods and solution-based methods. The vacuum-based approaches mainly involve thin film depositionusing sputtering and evaporation. These methods require relatively processing conditions such as hightemperature/vacuum systems and are often obtained with high cost. For this reason, solution-based methodsare being developed to significantly reduce manufacturing cost. Due to nanocrystals inks can be sprayed,spin or dip coated onto substrates directly and easily, many researchers have addressed on various kinds ofCZTS nanocrystals, and CZTS nanocrystals with different shape and crystallinity had been reported.In this dissertation, we successfully synthesized wurtzite CZTS nanospindles and sphere-like kesteriteCZTS by facile solution method. The dimensions of the as-obtained wurtzite CZTS nanospindles are about30-40nm in diameter and100-150nm in length. The sphere-like kesterite CZTS nanoparticles(NPs) withdiameter range of300-500nm were agglomerated by small CZTS nanocrystals. When used as Lithium-ionbatteries anode materials, the CZTS NPs exhibited stable lithium-ion insertion/extraction reversibility andlong cycle life. The main work of this dissertation completed as follows:(1) Wurtzite CZTS nanospindles were prepared through a facile one-pot method. XRD, TEM and SEM characterizations confirm the structure and morphology of the as-obtained CZTS nanospindles. The CZTSnanospindles show obviously enhanced optical and electrical properties. The CZTS nanospindles canharvest incident lights more efficiently(light-trapping effect), which can significantly improve thephotovoltaic properties of the CZTS films. Under same condition, the photocurrent gain in nanospindlesfilm is larger than that of nanocrystals film. These results indicated that CZTS nanospindles are favorableto increase current carrier concentration and improve electron transmission, which may improveperformance of photovoltaic devices in the future.(2) CZTS nanospindle film was selenized and then used to assemble CZTSSe thin film solar cells. Thenthe I-V tests were performed. The result of the tests was not desired, so more research is required beforethis materials system can fulfill the need for a next generation of high efficiency and low-cost photo-voltaicmaterials system.(3) Sphere-like CZTS NPs were synthesized by solvothermal method. SEM and TEM images revealedthat these sphere-like300-500nm CZTS NPs are were agglomerated by CZTS nanocrystals. When used asanode materials, these sphere-like CZTS exhibited stable lithium-ion insertion/extraction reversibility andlong cycle life. The electrochemical performance could be attributed to their hierarchical nanostructure aswell as the efficient charge transport induced by Cu or Zn. The electrochemical properties of thesesphere-like CZTS NPs implied its potential application as anode materials in the next generationlithium-ion batteries. |
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