Preparation And Optical Properties Of Al/N Co-doping TiO₂ Thin Films

Titanium dioxide(TiO₂)is currently one of the most promising semiconductor oxide materials,which can be used for photocatalytic degradation of potentially harmful organic dyes,wastewater degradation and air purification,as a light source for dye-sensitized solar cells(DSSCs).The wide band gap(3.2 e V)of TiO₂ makes it only respond to a small part of the solar spectrum(<10%).Therefore,improving the performance of TiO₂ by improving its optical properties to make it highly active in the visible light range is of great significance for effectively utilizing the entire solar spectrum.In this thesis,the structural characteristics,common preparation methods and characterization methods of TiO₂ thin films are introduced.The TiO₂ films,Al single doped TiO₂ films and Al/N co-doped TiO₂ films with different concentrations were prepared by an easy-to-operate and non-polluting sol-gel method.Different testing methods:X-ray diffraction(XRD),scanning electron microscope(SEM),ultraviolet visible spectrophotometer(UV-Vis)and photoluminescence spectrum(PL)were used to analyze the structural characteristics,the surface morphology and optical properties of the prepared samples,respectively.The experimental results are as follows:(1)All samples are in the anatase phase and grow along the preferred orientation of d(101)crystal plane.When the sample shows the best crystal quality,the surface is flat and dense,the defects are less,the response to visible light is good,and the band gap value is3.382 e V,the intrinsic TiO₂ sol concentration is 0.50 mol/L.(2)The doping of Al did not change the crystalline phase of TiO₂,and the sample was still anatase phase.When the Al doping amount is 3.00 at%,the absorbance of TiO₂ is the highest,and the band gap value is 3.249 e V.However,when the amount of Al doping is further increased,the performance of TiO₂ will decline due to excessive Al doping.(3)No characteristic peaks of Al,N and no other impurity peaks were found in co-doped samples,indicating that the prepared samples were relatively pure,and the N element did not change the crystalline phase of TiO₂,but the doping of N resulted in the reduction of diffraction peak and grain size.When the doping amount of N is 7.00 at%,the absorbance of the sample is the highest,the band gap is the smallest,and its band gap value is 2.873 e V.Orthogonal experiments have verified that when the intrinsic TiO₂ concentration is 0.50mol/L,the Al doping content is 3.00 at%,and the N doping content is 7.00 at%,the obtained TiO₂ films have the best optical properties.