Synthesis, Characteristic And Physical Property Of Titanate Nanobelts Films Sensitized By CuInS₂ Quantum Dots

In recent years, the energy crisis and environmental problems have become increasingly serious. As solar energy is an inexhaustible non-polluting energy, using photovoltaic solar energy is an important way to solve the energy crisis and environmental pollution.As new type nanomaterials, titanate nanomaterials with unique structure and properties have high light catalytic effect and special visible absorption and photoluminescence phenomenon. The traditional TiO2 only have ultraviolet absorption, which seriously limit the photovoltaic conversion efficiency. Therefore, titanate nanomaterials have widely applications in photovoltaic areas.Since the dye-sensitized solar cells proposed by Michael Gratzel, the study of the organic dyes have been a hot spot, however, its high cost, short life, performance instability limit the development of dye-sensitized solar cells. Therefore, using inorganic semiconductor quantum dots to replace organic dye in solar cells is a novel research direction.The band gap of CuInS2 is 1.5 eV, which is close to the optimum band gap for solar cell, and it has large absorption coefficient as a direct gap semiconductor. Moreover, CuInS2 is wildly considered by its special advantages, such as low cost, non-toxic, stable performance and so on. Thererfore, CuInS2 senmiconductor quantum dots sensitized solar cells have great prospect for future application.In order to obtain high conversion efficiency of solar cells, this paper proposes a concept of CuInS2 quantum dots sensitized one-dimensional titanate nanobelt solar cells. At first, we use alkaline hydrothermal process and screen-printing methods to prepare one-dimensional titanate nanobelt films, and then CuInS2 quantum dots are deposited on the surface of one-dimensional titanate nanobelts by self-assembly method. Finally, corresponding characterization and properties testing were taken to this light anode. The main contents and conclusion are as follows:1. Using alkaline hydrothermal process and screen-printing methods to synthesize one-dimensional titanate nanobelt films. The influences of the structure, morphology and properties of one-dimensinoal titanate nanobelt films at different screen-printing systems and heat treatment are discussed. It is shown that titanate nanobelts posse a rectangular cross-section with the length of 1-3μm, the width of 100-200 nm and the thicknees of 10 nm. When the screen-printing time is 3, the film thickness is 10μm, which is the best one for the anode in solar light. The corresponding UV-vis absorption and absorbing boundary edge are also the best. The theoretical calculation shows that the optical band gap of one-dimensional titanate nanobelt films is of 3.0 eV. It can obtained that the available thermal treatment temperature of the pure titanate thin films is of 350℃,while sampeles with the heat treatment temperature of 450℃appear anatase phase, which leads to change the film crystal structure and distance between the layer.2. CuInS2 quantum dots are prepared by two steps method. The results show that pure, well dispeared and evenly arranged CuInS2 quantum dots with the particle size of 19.3 nm may be synthesized by this method. The synthesized CuInS2 quantum dots with different sizes are controlled by different temperature, which may realize the optical absorption both in ultraviolet and visible light.3. CuInS2 semiconductor quantum dots sensitized one-dimensional titanate nanobelt films have been synthesized through MPA linker molecule, which is used to be an organic surfactant coupling agent. The XRD patterns and SEM images show that CuInS2 quantum dots with the particle size of about 10-20 nm are uniformly deposited on the surface of titanate nanobelts. By the increasing of sensitization time, the absorption contents of CuInS2 quantum dots increases, by following with the corresponding increasing of the UV-vis absorption intensity and edge of the sensitized films. However, UV-visible absorption intensity decreases when the sensitization time is 7 minutes. By the increasing of sensitization cycles, the absorption contents of CuInS2 quantum dots increase, and the UV-vis absorption intensity and edge of the sensitized films also increase. However, CuInS2 quantum dots almost completely cover on the surface of the titanate films when the sensitization cycle is 14, and the UV-vis absorption intensity decreases. Therefore, it could conclude that the best sensitization time is 5 minutes and the best sensitization cycle is 12.4. Using this sensitizd films as the anode electrode, the sensitized solar cells are fabricated, which posse the fill factor of 0.64 and photoelectric conversion efficiency of 1.058% with sensitization cycle of 12.