Controlled Synthesis Of Tungsten Oxide Micro-nanostructures Via Laser Ablation In Liquid And Their Photoelectric Performances

In the fast-developing modern society,optoelectronic technology plays a vital role.Photodetectors and electrochromic devices in photoelectric information conversion devices are widely studied,which have considerable application prospects in missile guidance,communication and monitoring,as well as smart window,information display and military equipment fields.Therefore,optoelectronic materials with excellent performance,low cost and environmental friendliness have always been hot topics in the field of materials research.Tungsten oxide,as a transition metal oxide semiconductor material,has potential for application of photodetectors due to its wide band gap and high absorption coefficient.However,current reports on tungsten oxide-based photodetectors have shown poor response speed.Tungsten oxide also is one of the earliest and most studied electrochromic materials because of its outstanding electrochromic properties.Compared to other electrochromic materials,tungsten oxide has excellent color efficiency and electrochromic stability,but its practical application is still limited by long response time.Thus novel tungsten oxide photodetector devices and electrochromic devices with fast response speed need to be studied urgently.In this thesis,laser ablation in liquid?LAL?combined with solvothermal synthesis method was used to fabricate tungsten oxide and its hydrate micro-nanoparticles.The influences of experimental parameters such as laser ablation time,reaction solution composition,solvothermal temperature and time on the microstructures and morphologies of the products were investigated.The synthesis and transformation mechanism of the orthorhombic WO₃·0.33H₂O and monoclinic WO₃ were clarified.The results show that extending the laser ablation time significantly increases the yield.The product growth rate was increased by increasing the solvothermal temperature.The structures and morphologies of the products are sensitive to the composition change of the reaction solution.The controllable preparation from orthorhombic WO₃·0.33H₂O to monoclinic WO₃ was realized by regulating the composition of the solution.In addition,the morphologies of irregular plates,hexagonal plates,rectangular rods,rhomboid stacks,and peach-pit-like particles were obtained at different ethanol/water ratios.And the hexagonal plates,hexagram columns,stacked prismoids,and irregular stacks were obtained under different ethanol/hydrogen peroxide ratios.High-purity and high-crystallinity WO₃·0.33H₂O and WO₃ obtained by LAL were centrifuged at high speed on an interdigital electrode to form tungsten oxide and tungsten oxide hydrate-based photodetector devices,and the photoresponse performance was explored.The annealing process was performed to enhance the performances of the photodetectors by eliminating the crystal defects and improving the film quality.The photoresponsivity and response speed of the tungsten oxide photodetector were improved,and the response time was as short as 5.8 s.An amorphous/crystalline complex[WO₂?O₂?H₂O]·1.66H₂O structure porous film was prepared onto FTO substrate by electrophoresis deposition of the tungsten oxide colloidal solution obtained by LAL.The tungsten oxide hydrate electrochromic device was constructed and its electrochromic properties were investigated.The synergetic effect of the unique amorphous/crystalline complex structure and mesh-like porous structure of as-deposited tungsten oxide hydrate film facilitates the ion insertion and extraction,improving the electrochromic performance of the tungsten oxide hydrate films.The coloration and bleaching time of the obtained tungsten oxide hydrate film were 7.8 s and 1.7 s,respectively.The reversibility parameter value was calculated to be 96.9%.