Synthesis Of Low Dimensional Semiconductor Materials And Their Applications In New Energy Devices

As breakthroughs and innovations are continuously to be made in nanotechnology, low dimensional semiconductor materials become more highlighted in all kinds of new type devices because their unique nano structures and exellent electron transfer characteristic. Among these devices, new energy devices are the hot focus for certain. In this thesis, several typical synthesis methods for low dimensional semiconductor materials and their applications in new energy devices were investigated scientificly, and devices such as field effect transistor (FET), lithium ion battery (LIB), dye-sensitized solar cell (DSSC) and supercapacitor (SC) were fabricated according to various nano structures of these materials, showing oustanding performances, including flexible devices. The main results can be summarized as follows.By using chemical vapor deposition (CVD) method, low dimensional indium sulfide with variety of nano morphology and structures and gallium selenide nanowires were synthesized. Characterization results of gallium selenide nanowires indicate their large aspect ratio and rich production, which is very suitable for the fabrication of FET based on single nanowires. Back gate structured FET based on Si/SiO2substrate was fabricated by some technological processes such as photoetching, etc. Electronic property measurement results of the FET indicate that the gallium selenide nanowires-based FET shows a significant p-type semiconductor property, Schottky barrier exists in the contact interface between the nanowires and channel resulting in a large resistance, and small changes in surrounding environment will lead to enormous negative effects on the testing results. The above conclusions can provide a certain reference for the synthesis of low dimensional indium sulfide and gallium selenide nano structrues and their applications in electronic devices.By using repeated hydrothermal synthesis method, a new type of zinc oxide with braiding nano structures with carbon cloth substrate was synthesized after calcining at400℃for2hours, which were used as the negative electrode material for LIB, and then the LIB was successfully fabricated and packaged. Characterization results demonstrate the purity and conformity of the products before and after calcining. Testing results of the repeated charge-discharge and circulatory property for LIB indicate that it owns a good reversibility, the discharge capacity for the first cycle is1450mAh g-1under a scanning rate of0.5mV/s, which is higher than the theoretical value of the specific capacity for zinc oxide,978mAh g-1, and the charge capacity for the first cycle is1067mAh g-1. After ten cycles the specific capacity tends towards stability at about600mAh g-1, and keeps on without obvious decrease even after130cycles, with a coulombic efficiency keeping at about100%in the whole cycle process. The LIB also shows significant cycle stability between0℃～60℃even at a high humidity of90%.By calcining the braiding nano structured zinc oxide at800℃for5hours to remove the carbon cloth substrate, the hollow braiding nano structured zinc oxide was obtained, which still keep the flexibility of the carbon cloth, and was used as the anode material for DSSC. Characterization results proof that the carbon cloth has been removed completely. Testing results for the fabricated DSSC show that the conversion efficiency reaches to0.38%after TiCl4treated, and the short-circuit current density, fill factor and open-circuit voltage have been greatly improved by TiCl4treatment than that without TiCl4treatment. The best photoresponse range is450～600nm, and peak value of the conversion efficiency reaches to1.2%after TiCl4treatment in this range, increasing by20%than that without TiCl4treatment. Lifetime for DSSC can be as long as162ms, which is a qualitative leap, fully indicating the optimization effert of TiCl4for the anode of DSSC.By using the pre-produced zinc oxide on carbon cloth as the template, after dipping in nickel nitrate solution and calcining, and then dipping in KOH solution, the zinc oxide template was removed successfully, so hierarchical nickel oxide nanosheets were synthesized, which were used as the electrode material for SC. Characterization results show that plenty of tiny holes appear in the hierarchical structure of nickel oxide after calcining, which can greatly increase specific surface area and ensure the promotion of the SC performance. The fabricated liquid state SC with3M KOH electrolyte exhibits obvious pseudocapacitance character, excellent reversibility and stability. Specific capacity for the liquid state SC can reach to842mF/cm2at current density of1mA/cm2, and testing data further demonstates the necessity to remove zinc oxide. The fabricated flexible solid state SC with PVA-KOH electrolyte exhibits obvious double-layer character, excellent reversibility and stability. Specific capacity for the flexible solid state SC can reach to20mF/cm2at current density of0.1mA/cm2, and can still maintain a high performance at different angle of bending even when twisting. The LED light was successfully lightened by the flexible solid state SC, showing a certain capacity for application in practice.