Preparation And Properties Of Ti-Based Flexible Dye Sensitized Solar Cells With Nanotube Array Interface Layer

Dye-sensitized solar cells (DSSCs) have attracted great interest in academic research and industrial applications because of the high conversion efficiency, low cost and simple fabrication processes. During recent decades, many researchers have been devised to make DSSCs with flexibility to extend their applications. Replacing the rigid glass with polymer conductive substrate or metal foil is a well-know way to make the fabrication of light weight, flexible and low-cost DSSCs possible. However, the thermal instability of polymer materials limits the sintering temperature of photoanode to below150℃, which results in the poor interconnection between TiO2particles. Ti foil is used as the photoanode substrate due to their good flexibility, low cost, low resistance and high temperature sinterability. However, the highly transparent flexible counter electrode (CE) is crucial because of the back-illuminated structure for the Ti-based DSSC. Moreover, the electrical contact between the TiO2film and the Ti substrate is poor. Therefor, improving the contact adhesion between the Ti substrate and the mesoporous TiO2film is an efficient method to enhance DSSCs performance.In this study, some works have been done to solved these problems:(1)High transparent and catalytically active Pt counter electrodes were prepared on conductive plastic substrate by ion sputtering deposition with different sputtering time. The DSSCs composed of Pt CE with sputtering time of20s shows the highest conversion efficiency of4.0%at AM1.5simulated full sunlight. The result showed that Pt CE by ion sputtering deposition are high catalytically active and good transmissible. (2) The titanium foil were used to prepared TiO2nanotube by anodization, which could prepare the high density TiO2nanotube arrays with regular and orderly structure. According to the principles of anodization, the influencing factors were studied for formation of TiO2nanotubes, that were applied electrolyte, voltage and time of anodic oxidation. The image of FESEM showed that the average length of TiO2nanotubes based on NH4F electrolyte were about1.3-3μm and the outer diameter were about60-70nm. The average length of TiO2nanotubes based on HF electrolyte were about150-285nm and the outer diameter were about60-70nm.(3)The Pt/ITO-PET by ion sputtering deposition were used as flexible counter electrode. The The photoanodes with TiO2nanotubes blocking layer were assembled with Pt/ITO-PET to make DSSCs. The influence of screen printing layers on the photovoltaic properties of DSSC with back-illumination is investigated. The best cell efficiency as high as5.1%was achieved with the mesoporous TiO2film thickness of17μm based on screen printing layers of8times. Also, the effect of the highly ordered TNTs array on Ti substrate surface properties and the performances of DSSCs were investigated. The DSSC with TiO2nanotube layer in NH4F electrolyte anodized at30V with time of60min showed a highest short-circuit current density of9.4mA cm-2and a energy conversion efficiency of5.1%. Finally, the TiO2nanotube were treated by TiCl4solution, which improves the photocurrent and photovoltaic performance. The cell efficiency as high as5.1%was achieved in the presence of TNTs blocking layer in NH4F electrolyte treated by TiCl4solution. Meanwhile, the efficiency of DSSC based on TNTs blocking layer in HF electrolyte were of5.0%.