Synthesis Of Novel Semiconductor Nanocrystals And Their Optoelectic Properties

In the past few years, semiconductor nanocrystals have been extensively investigated due to their unique physical and chemiscal prorerties. With the continuously deepening understanding of the synthesis and properties of semiconductor nanomaterials, they have been applied to optoelectronic devices, photocatalytic and biomedicine. Today, study on semiconductor nanomaterials has become one of the hot fronts of materials science with great application promise in addressing the clean energy and environmetal crisis. This dissertation focuses on the solution-phase synthesis of the new inorganic semiconductor nanocrystals, such as the multicomponent Cu2Ge(S3-x,Sex) nanocrystals, single-crystalline CdsP2nanowires, CdTe/TOPO core-shell nanowires, and Sb2Se3/Sb heterostructure. We have further assessed their fundmental properties investigated their application potentials in optoelectronics:(1) The multicomponent Cu2Ge(S3-x,Sex) semiconductor alloy nanocrystals were synthesized successfully via a colloidal solution-phase method, in which the contents of S and Se can be varied across the entire compositional range (0≤x≤3). The nanocrystals exhibits band gaps ranging from2.16eV to1.20eV with increasing the Se composition in the products. The nanocrystals showed the the single crystal structure and uniform size. Cyclic voltammogram (CV) measurement revealed these Cu2Ge(S3-x,Sex) nanocrystals show typical p-type semiconducting behavior, thus solar cells were fabricated using Cu2GeS2Se as model light absorbers with n-type CdS nanorods as electron-transport materials, showing significant photo-to-electric conversion efficiency of0.20%under AM1.5illumination. These results should be favorable for improving our understanding of their basic properties and their device applicability.(2) The Cd3P2nanowires were synthesized using Bi nanoparticles (a low melting point metal) as catalysts in a relatively low temperature via a solution-liquid-solid method. The growth conditions of the nanowires were studied in detail. The nanowires showed the single-crystal structure, controllable length, significant quantum size effect. The photodetector devices were fabricated using the Cd3P2nanowires as building blocks, showing their application potentials in optoelectronic devices. (3) The Core/Shell CdTe/TOPO nanowires with variable thickness of shell were synthesized by depositing TOPO layers around single-crystal CdTe nanowires that were preformed by solution-liquid-solid approach. Conductivity measurement based on an individual core/shell nanowire confirmed that the shell of TOPO based complex exhibited an insulation behavior, which may found application in nanoelectronics.(4) The heterostructures of Sb2Se3nanowires/Sb nanosheet were synthesized successfully via a colloidal chemistry. The morphology and composition of the heterstructures were studied by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and scanning transmission electron microscope image (STEM). The photoelectrochemical response of the Sb2Se3/Sb heterstructures has been measured.