Fabrication Of TiO₂ Nanotube Arrays And Its Application In Dye-sensitized Solar Cells

In order to promote the development of new energy sources, environmental control and other fields, TiO2 nanotube arrays with excellent optical properities have been widespreadly concerned. The objective of this paper is to study the anodic oxidation process, and frabricate TiO2 nanotube arrays with excellent structure and morphology. After all, we researched the application of TiO2 nanotube arrays in dye-sensitized solar cells(dye-sensitized solar cell, DSSC).The influence of electrolyte in the fabrication of TiO2 nanotube arrays is essential. We fabricated TiO2 nanotube arrays by anodization in HF system electrolyte, glycerol system electrolyte, glycol system electrolyte, respectively. In addition, we analyzed the nanotube structural features. The results show that high pH of HF system electrolyte causes nanotube with low tube length. Large viscosity of glycerol electrolyte system makes the uneven nanotube diameter and slow filming rate. Long tube length nanotube film can be obtained with fast growth rate only in glycol system electrolyte.Base on the above results, the impact of different process parameters on the TiO2 nanotube arrays structure was studied in glycol system electrolyte. The results demonstrate tube diameter and length growth with the increasing of NH4 F content, H2 O content, anodization voltage and anodization time. Among those parameters, the anodization time can more precisely control nanotube array parameter. According to those studies, we also found that the change of any parameter can cause the emerge of upper nanowire bottom nanotube composite structure. The special structure was studied through two-step anodization, the result show that it can be obtained based on the moderate etching rate of the electrolyte and the selective etching of nanotubes.We have assembled front-side illuminated and back-side illuminated DSSC. The back-side illuminated DSSC which base on Ti foil substrate with 17μm~23μm length nanotube arrays, shows that the most excellent photoelectric performance(Jsc=9.2mA/cm2,, Voc=0.6V, FF=0.6, η=3.35%) was obtained in the DSSC with 20μm tube length. We transfered nanotube film to FTO by two-step anodization self-detaching method, and assembled the front-side DSSC, the photoelectric performance which based on 20μm length TiO2 nanotube arrays(Jsc=11.8mA/cm2, Voc=6.2V, FF=0.6, η=4.39%) is better than back-illuminate. This improvement of photovoltaic performance was decided the front-side illuminated DSSC avoiding light loss in electrode and electrolyte.