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The existent research literature of Dye Sensitized Solar Cells (DSSC) is mainly focused on the dye but there are very few studies focused in the semiconductor. Here, we present the performance of hydrogen titanate nanotubes (HTNT), showing an enhancement of the solar cell efficiency from 5.95% to 7.63%, respect to anatase as photoelectrode. This enhancement could be explained in terms of open-circuit voltage, directly associated to the value of the HTNT band gap (E g  = 3.3 eV), the relative position of the edge conduction band; and the increase of the short-circuit current, directly associated to the enhancement of the specific area of the photoelectrode. All these characteristics are in very good concordance with our theoretical modelling of the system, based on First Principles calculations. We expect that this system could be further characterized, utilizing different dyes or absorbers, in order to evaluate the potential use of hydrogen titanate nanotubes for solar cell applications. [ABSTRACT FROM AUTHOR]

In this work we present the synthesis, structural, morphological, optical and electrochemical characterization of sodium titanate nanotubes (NaNT) obtained by hydrothermal means. According to our detailed structural study, we found that a Na 2 Ti 2 O 5 ·H 2 O layered crystalline phase with [TiO 5 ] pyramidal square base coordination, utilized as a building block of the nanotubes, explains satisfactorily the experimental results. This is a very important aspect, since the bibliography does not always provide structural information about titanate nanotubes. With respect to the formation mechanism we highlight the crucial role of the post treatment washing in the final crystalline structure of the nanotubes. Simulated X-rays powder diffraction patterns (XRPD), based on real size nanotubes models, were refined with experimental data. Building blocks for the NaNT model were inferred from computational simulations, by means of Density Functional Theory. The obtained tube's model characteristic dimensions were also consistent with SAXS and TEM analysis. In addition, our SAXS analysis suggested that the presence of humidity in the cavities of titanate nanotubes is progressively lost at the 80–100 °C temperature range, in good agreement with thermogravimetric analysis. Electrochemical impedance spectroscopy analysis for dried samples in the temperature range, studied under cooling conditions, revealed a single ionic transport mechanism, probably associated to the in-between [TiO 5 ] layers ion transport. However, a secondary process was observed for non-dried samples, during heating conditions, that could be associated to the ionic transport along the water filled tube's cavity, consistent with SAXS analysis. In summary, this work shows an integral approach, through theory and experiment, in order to understand the effect of the structure on the physical and electronic properties of the system. • Crystalline phase Na 2 Ti 2 O 5 ·H 2 O as building block for sodium titanate nanotube. • Morphological and structural characterization of NaNT. • Computational simulation of structural, vibrational and electronical properties. • Two different sodium transport characterization in NaNT. [ABSTRACT FROM AUTHOR]

Abstract In this work we present the comprehensive design of lithium titanate nanotubes (LiTNT) as semiconductors for DSSC photoanodes. The synthesis and characterization of Li 1.82 Na 0.18 Ti 3 O 7.nH 2 O nanotubes was performed and a prototype of cell using this material was assembled. The cell exhibited a 7.7% efficiency and a relatively high open circuit voltage, Voc = 0.72 V. In comparison with previously obtained hydrogen titanate nanotubes (HTNT), improvements have been achieved, like better charge carriers' lifetime and lower series resistance. In order to study this system, we carried out previous DFT simulations for this lithium titanate nanotubes through different model's complexity levels which were able to correctly predict its properties. Due to the improvements achieved this system would encourage further studies with the aim to explore its potential for solar cells applications. [ABSTRACT FROM AUTHOR]