Hydrothermally native defect induced transparent p-n TiO2 homojunction diode

摘要

Abstract This study aims to prepare transparent defective p-type TiO2 films using defects chemistry via the hydrothermal method, showing that the metal vacancies (VTi) may be easily presented into undoped oxide, then constructing a p-n homojunction diode. The defective TiO2 depicts the p-type conductivity with a high charge mobility which was verified via the Hall Effect measurement. The influence of growth time upon the TiO2 nanorods' morphological, structural, and optical properties was investigated and analyzed using Field Emission Scanning Electron Microscopy (FESEM), X-ray Diffraction (XRD), X-Ray Photoelectron Spectroscopy (XPS), and ultraviolet–visible spectroscopy methods (UV–VIS). The measurements of XPS were utilized for investigating the chemical conditions of the constituent elements and the XRD analysis of deposited films for (24 h) at (180 °C) have confirmed the formation of the polycrystalline-tetragonal phase anatase as a major phase with a minor rutile phase. The FESEM measurements of TiO2 films evinced the grass shape nanostructure with a diameter range (of 26–76) nm for the prepared films with different growth times. The stoichiometry ratio of (Ti) and (O) in TiO2 films was confirmed by (EDX) analysis to be 2:1. Optical properties have been investigated, the transmittance, absorbance, and energy gap at various growth times were measured and computed, and the results manifested that the rod length reduced the transmittance, while it augmented the absorbance with slight change in the energy gap, the PL intensity of defective p- type TiO2 smaller than of n-type. The p-n homo-junction demonstrated the distinct diode-like behavior with ideality factor n = 32.069. These findings could have far-reaching consequences for the development of nanostructured metal-oxide solar cells, photo-catalysts, LEDs, photodiodes, and photo-electrochemical devices.