Hydrothermal Fabrication of Hierarchically Anatase TiO2 Nanowire arrays on FTO Glass for Dye-sensitized Solar Cells

Abstract

Hierarchical anatase TiO2 nano-architecture arrays consisting of long TiO2 nanowire trunk and numerous short TiO2 nanorod branches on transparent conductive fluorine-doped tin oxide glass are successfully synthesized for the first time through a facile one-step hydrothermal route without any surfactant and template. Dye-sensitized solar cells based on the hierarchical anatase TiO2 nano-architecture array photoelectrode of 18 μm in length shows a power conversion efficiency of 7.34% because of its higher specific surface area for adsorbing more dye molecules and superior light scattering capacity for boosting the light-harvesting efficiency. The present photovoltaic performance is the highest value for the reported TiO2 nanowires array photoelectrode.

Maximizing omnidirectional light harvesting in metal oxide hyperbranched array architectures

“…In other words, more effective photon capturing in the visible region and more dye molecules anchoring on the films will increase the probability of photon-dye molecule interaction, thus leading to high light-harvesting efficiency and high photo-generated current. Hence, an impressive efficiency of 9.09% was obtained for the devices based on TNW-NS-NR photoanodes of 16 mm in thickness, which is above the threshold for reported efficiency of devices fabricated similarly with N719 dye-sensitized TNW photoelectrodes of similar film thickness 23 . The details about the reproducibility of DSSCs with best performance are listed in Supplementary Table 4, which further manifest the reproducibility of the current samples and performances are quite good and the results are reliable.…”

“…Figure 1b,c shows SEM images of a cross-sectional view and corresponding individual NW, respectively. Obviously, a uniform and well-separated NW array with a smooth surface and a length of B16 mm grow almost vertically from the substrate during a hydrothermal reaction for 3 h, confirming their preferential growth along the y-axial (001) direction over the x-axial (110) direction in the case of the potassium titanium oxide oxalate dehydrate (PTO)/H 2 O/diethylene glycol (DEG) hydrothermal system 23 . The prepared NWs show a bundle-like morphology consisting of several slim wires (B70-80 nm in diameter) (Fig.…”

“…Via variation from pure 1D backbones to complex 3D monoblocks, the hyperbranched array (TNW-NS-NR) film exhibits substantially enlarged surface area, for which a twofold increase of the dye-loading capacity is observed compared with the parental TNW counterpart. Consequently, an enhanced absolute full-sun efficiency of 9.09% is attained for a TNW-NS-NR-based cell, which is 77% higher than the pure TNW-based device (5.15%) and 24% higher than the highest value reported for hierarchical TNWs based cell (7.34%) with a similar film thickness 23 . The enhancement could primarily arise from the synergistic effects of enlarged dye loading and improved light scattering, which maximize the light-harvesting capability of the array architectures.…”

“…One of the approaches to increase the surface area for improving the device performance is to increase the length of 1D nanostructures 20 . Another classical solution is to decorate the 1D nanostructures with dendritic NR branches [21][22][23] . For example, several studies regarding long NWs or the assembly of 1D nanostructures into three-dimensional (3D) hierarchical tree-like or bush-like branched NW structures have been reported [24][25][26][27][28][29] .…”

Preparationand Characterization of Rutile-anatase Hybrid TiO2Thin Film by Hydrothermal Synthesis

“…In an advanced method, Wang et al [36] attached TiO2 nanobranches to the nanorods to increase the surface area and achieved a DSSC power-conversion efficiency of 3.75% even with nanorods that had heights of 3 µm. Nevertheless, it has been known that these forms of rutile TiO2 are inferior to anatase TiO2 in terms of DSSC power-conversion efficiency, and it is very difficult to grow anatase TiO2 nanorods vertically on FTO glass because of the large lattice mismatch (~19%) between anatase TiO2 and FTO [37,38]. Therefore, a TiO2 colloid solution must be spin-coated onto the FTO glass in order to synthesize the layer of nanostructured anatase-phase TiO2 [39].…”