Studies On Electrical And Optical Properties Of TiO₂and Y₂O₃nano-materials

This work is focused on the investigation of optoelectroic properties based on TiO2and Y2O3nano-materials. The main contents of dissertation include three parts.1. A photocatalytic strategy was developed to synthesize colloidal Ag-TiO2nanorod composites and the mechanism of the formation for Ag-TiO2nanorod composites was investigated.(?) Under UV illumination, TiO2nanorods produces electrons which reduce Ag (Ⅰ) precursor and deposit multiple small Ag nanoparticles on the surface of TiO2nanorods. Prolonged the time of UV irradiation induces an ripening process, in which the smaller nanoparticles is dissolved by photo-generated oxidative species and then redeposited onto one largest and more stable particle attached to each TiO2nanorod. The size of the Ag nanoparticles can be precisely controlled by varying the irradiation time and the amount of alcohol additive.(?)The Ag-TiO2nanorod composites were used as electron transport layers in the fabrication of organic solar cells, and showed notable enhancement in power conversion efficiency (6.92%) than pure TiO2nanorods (5.81%), which is attributed to the improved electron extraction.2. For the photocatalytic synthesis of gold nanoparticles assisted by TiO2nanorods, the mechanism was studied carefully by change the reaction temperature, UV irradiation time and amount of the TiO2nanorods.(?) Monodispersed gold nanoparticles were synthesized through a photochemical reduction approach using TiO2nanorods as the photocatalysts.(?) The formation of Au nanoparticles ccould be divided into three processes:the reduction of Au(Ⅲ), nucleation and growth of the gold seeds. The first step mainly depends on the temperature. And nucleation and growth of the gold seeds processes highly depend on the electrons generated on the TiO2nanorods.3. Er and Yb co-doped Y2O3nanoparticles were prepared by using a coprecipitation method followed by a post-thermal-treatment. In order to study the upconversion properties of the Y2O3:Er, Yb nanoparticls, the defects were induced and removed by surfactant and calcination. Moreover, the mechanism of color tuning was investigated.(?)The green (2H11/2,4S3/2→4I15/2) and red emission (4F9/2→4I15/sn) intensity can be effectively tuned by varying the surfactant concentration, which can induce the defects in the as-obtained products. The probability of quenching from4F7/2,2H11/2, and4S3/2to4F9/2could be increased as the number of defects introduced by the surfactant increases, and thus the ratio of red to green emission is also changed.(?) After removing the defects via high temperature calcination, the green emission (2H11/2,4S3/2→4I15/2) and red emission (4F9/2→4I15/2) of Er ions are enhanced selectively, which leads to that the color of upconversion emittion is tuned from red to green.