The Study On Structural Optimization, Modification And Sensitized Solar Cells Of TiO₂Nanotube Arrays

TiO₂nanotube arrays, which were prepared with anodization, were widelyused as photo-anode of dye-and quantum-dot-sensitized solar cells due to theirhigh specific surface area and excellent one-dimensional properties. However,low power conversion efficiency, poor electron transport and expensivesensitizer are still the issues for the TiO₂nanotube-based solar cells. In this work,aiming to improve the power conversion efficiency and lower the cost of theTiO₂nanotube-based solar cells, we investigated the decoration andmodification of photo-anode based on TiO₂nanotube arrays systematically.The details are as below.The influence of the composition of electrolyte, anodic duration and timeson the morphology and structure of TiO₂nanotube arrays have been investigated.The highly ordered TiO₂nanotube arrays with smoother surface and free debriswere obtained with a second-anodization under optimization. Compared withthat of the TiO₂nanotube arrays before optimization, the power conversionefficiency exhibits an enhancement of36%.We report for the first time a simple surfactant-assisted vacuumimpregnation （SVI） approach for controlling assembly of sub-10-nm TiO₂NCsinto NTAs as a more efficient photoanode for DSSCs. Double polymersurfactants were introduced to guide the NC assembly process and prohibit theNCs from over-agglomeration. Through the double-layer isolation by thelong-chain organic molecules, we are capable of achieving well-dispersed NCdeposition on the nanotube walls. The performance of DSSCs was greatimproved with the filled TiO₂nanotube arrays compared with that of un-filledone. By adjusting the content of filled nanoparticles, the power conversionefficiency was1.94times to that of the bare one. Highly [001] oriented TiO₂nanotube arrays were successfully prepared bycontrolling the recipe of anodization and process of post-treatment deliberately.The results reveal it shows excellent electron transport compare to non-orientedTiO₂nanotube arrays. It were detached and transferred to FTO successfully andunder front-illuminate, the enhancement of29%in power conversion efficiencywas obtained compared with non-oriented TiO₂nanotube arrays.Novel Cu₂ZnSnS₄（CZTS） quantum dots vary from3.1nm to17nm wereprepared with microwave-assisted route. The results of XRD, Raman, HRTEMand XPS show that it was the Kesterite CZTS quantum dot. The quantumconfinement effect was observed for CZTS quantum dots of3.1nm. CZTSquantum dots were used as sensitizer of TiO₂nanotube-solar cells and it showthat the short-circuit current density of the CZTS quantum-dot-sensitized solarcells increase with the decrease of diameter of quantum dots. Moreover, thedifference of J-V performance and electron transportation between TiO₂nanoparticle-and TiO₂nanotube-based solar cells sensitized with CZTSquantum dots were discussed. The prototype of the environmental friendlylow-cost CZTS quantum dot-sensitized solar cells was a promising structure inthe next-generation solar cells.