Preparation And Application Of TiO₂-Based Thin Film Materials

Because of its excellent physical and chemical properties,Ti O₂was widely used in semiconductor functional fields such as solar cells,gas sensors,photocatalysis,and photodetectors.It is a star material in the field of semiconductor materials research today.However,the current performance of Ti O₂-based functional materials is not sufficient for practical applications,and there are still many problems to be solved,such as low photoelectric conversion efficiency,high operation temperature,and low on/off ratio.Therefore,in view of the above problems,this thesis will study new Ti O₂-based functionalized materials and optimize the performance of Ti O₂-based functionalized materials by means of morphology control,energy band engineering,material compounding and device design.The specific research content is as follows:In chapter two,a CdS quantum dots/ZnO nanorods/Ti O₂nanosheets hierarchical heterostructure film was synthesized on FTO conductive glass by hydrothermal method and successive ionic layer adsorption reaction method as photoanode material for photoelectrochemical solar cells.The experiment results show that the Zn O nanorods can significantly increase the specific surface area;the sensitized Cd S quantum dots can significantly increase the light absorption capacity;the heterojunctions formed between the Ti O₂nanosheets,Zn O nanorods and Cd S quantum dots can effectively promote photogeneration carrier migration and inhibit electron-hole recombination.In addition,it is worth noting that Zn O nanorods tend to grow only on the low-energy{101}facet of Ti O₂nanosheets and can build a special energy band structure between them,which can effectively shorten the electron conduction path and provide a greater charge driving force to promote the separation of photogenerated electron-hole pairs.Under the synergistic effect of the above structures,the short-circuit photocurrent density of the best-performing Cd S/Zn O/Ti O₂film can reach 12.1 m A/cm²,which has greatly improved in comparison to the single Ti O₂film.In chapter three,the etched FTO conductive glass was designed as a new-type gas-sensing test electrode,and the Ti O₂nanorod material was grown in situ based on the new FTO electrode as a gas sensing material.As a result,a novel Ti O₂-based gas-sensitive element was prepared.Due to the synergistic effect of the multi-directional force generated by the change of the conductive layer of the FTO electrode,the Ti O₂nanorods exhibit a special double-layered bridge-like morphology.Gas sensing tests showed that all samples obtained at different growth times had excellent gas sensing response to low-concentrations NH₃at room temperature.Among them,the Ti O₂nanorods sensor obtained at 6 h has the highest gas sensitivity response to 50 ppm NH₃,and its corresponding value can reach 61%.In addition,this work discusses the growth mechanism of the special double-layer bridge-like morphology,the gas sensing response mechanism,and the effect of humidity on the gas sensing performance,and proposes a reasonable guess for the excellent selectivity of Ti O₂sensor to NH₃.This work proposes a new-type gas-sensing electrode and a special double-layer bridge-like morphology that can provide an important research ideas for the design of a novel low-cost room-temperature gas sensor.In chapter four,a TiO₂nanorod array thin film was grown in situ on the surface of FTO conductive glass by hydrothermal method,and an FTO conductive glass on the other side of the sample surface was fixed with a jig as a counter electrode to prepare a sandwich-type photodetector.The photodetector can detect ultraviolet light at a working voltage of 0 V,which has the advantages of self-powering.The effect of electrode materials on photodetection performance has been explored.When the Ni sheet is used as the counter electrode,the on/off ratio of the photodetector to ultraviolet light is increased from 67 times to 638 times compared with the FTO as the counter electrode.This work provides a simple method for the preparation of asymmetric MSM-type photodetector and has achieved improved photodetection performance,which can provide a possible idea for the preparation of new-type photodetector and the improvement of photodetection performance.