Preparation And Photoelectric Properties Of Quantum Dot-sensitized3D TiO₂Nanotube Array

Due to their high surface-to-volume ratio and vertical orientation on titanium substrate, highly ordered TiO2nanotube arrays showing the advantages on light absorption, charge transport and electron-hole separation have been widely used. Generally,2D TiO2nanotube arrays were obtained on Ti foil by anodization. However, TiO2nanotube arrays on an opaque Ti substrate has limited their application in front-side illuminated solar cells. In addition, TiO22can not effectively utilize sunlight due to its wide band gap. Therefore, this study devotes to fabricating a novel structure of TiO2/Ti mesh photoelectrode and investigating the photoelectric properties of the TiO2/Ti mesh photoelectrode modified by quantum dots.In this paper,3D TiO2nanotube arrays were prepared by electrochemical anodization in an ethylene glycol electrolyte containing0.3wt%NH4F and2wt%H2O. The morphologies of TiO2nanotube arrays prepared at different oxidation time, different oxidation voltage were characterized by scanning electron microscope. The results show that increasing oxidation voltage and oxidation time lead to an increase in the tube length. Besides, the oxidation voltage and oxidation time can also change the surface morphology of TiO2/Ti mesh photoelectrodes. The photoelectric properties of TiO2/Ti mesh photoelectrodes fabricated at different formation voltage and time length were investigated. The results show that the TiO2/titanium mesh photoelectrode anodized at60V for1h exhibits the highest photocurrent density (58?A/cm2) and photoconversion efficiency (5.9%) under the UV light illumination (1mW/cm2). The effect of substrates on the photoelectric performance of TiO2nanotube arrays has been studied. In comparison to TiO2/Ti sheet photoelectrode, TiO2/Ti mesh photoelectrode demonstrates better photoelectric properties. The photocurrent per mass of TiO2/Ti mesh photoelectrode is about3.4times of that of the TiO2/Ti sheet photoelectrode. Through investigating the photoelectric performance of TiO2/Ti sheet photoelectrode and TiO2/Ti mesh photoelectrode under the different illumination angles, we found that the variation of photocurrent of TiO2/Ti mesh photoelectrode with illumination angles is much less sensitive than that of TiO2/Ti sheet photoelectrode, indicating great potential applications in solar cells.In order to broaden the photoresponse range of TiO2nanotube arrays, quantum dot modifying method has been used. PbS/TiO2, CdS/TiO2and CdS/PbS/TiO2photoelectrode were prepared by successive ion layer deposition and reaction. The influence of different quantum dots on TiO2/Ti mesh photoelectrode has been investigated. The results indicate that PbS/TiO2photoelectrode shows a significant improvement in photocurrent density, which is about32.27and2.77times than That of the pure TiO2and CdS/TiO2photoelectrodes, respectively.By comparing the effect of single quantum dots and quantum dots co-sensitization on T1O2, the results show that the CdS/PbS/TiO2photoelectrode has the best photoelectric properties. Upon100mW/cm2xenon irradiation, CdS/PhS/TlO2photoelectrode show the highest photocurrent density of5.86mA/cm2, which is about3.35and1.21times than that of CdS/TiOa and PbS/TiO2photoelectrodes, respectiely. This result can be ascribed to the excellent light responsiveness of complex quantum dots sensitized and a good match between the energy levels of quantum dots and substrate material.