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Heart diffraction glasses4/4/2023 Up to now, several techniques, including vapor deposition, (23) pulsed-laser deposition, (24) and atomic layer deposition (ALD), (25) template, (26,27) and hydrothermal methods, (28−30) have already been employed for the synthesis of hierarchically structured TiO 2 with controlled morphologies and architectures. (19−22) However, in many cases, the formation mechanism of these well-designed hierarchical structures is far less understood and sometimes even not considered, which thus is still an urgent issue to be tackled in this field. Alternatively, three-dimensional (3D) hierarchical TiO 2 architectures consisting of 1D building blocks have attracted researchers′ considerable attention since the elaborately designed nanostructures could often simultaneously functionalize integration of the virtues of lower dimensional structures, such as zero-dimensional (0D) and 1D nanomaterials, which thus provides the greatest possibility of improving the photovoltaic performance. (11−18) In comparison with the randomly organized network, though one-dimensional (1D) nanomaterials could offer fast electron transport highways, the fundamental drawbacks of a low internal surface area and the large void spaces between adjacent nanostructures become the main factors hindering performance improvement. Various TiO 2 structures in the forms of nanotubes, nanorods, nanowires, nanofibers, nanosheets, and nanoflowers have been reported. (9,10) In this case, rutile TiO 2 is also an ideal candidate for a DSC device on the condition of taking full advantage of its virtue and deliberately mitigating the drawbacks by elaborately tailoring the morphology features. (6−8) Besides, rutile TiO 2 also possesses some superior physical properties over the anatase phase, especially the enhanced light-scattering properties in virtue of its higher refractive index, which is obviously beneficial from the perspective of efficient photon harvesting. Recent studies have, however, demonstrated that rutile TiO 2-based solar cell devices can also achieve a comparable V OC to those made with anatase, and substantially enhanced electron transport has also been verified in one-dimensional (1D) rutile TiO 2 nanostructures, which largely eliminates the concerns of the researchers interested in rutile phase TiO 2. TiO 2 has three different polymorphs: anatase, rutile, and brookite, and the TiO 2 rutile phase is prejudicially considered to be inferior to the anatase phase and thus often ignored in DSCs, mainly due to its more positive conduction band edge potential, which is regarded to be detrimental for the achievement of a higher open-circuit voltage in DSCs. Great attention has been therefore paid to controlling the crystal phase, shape, dimensions, and surface properties of nanostructured TiO 2 materials to construct outstanding photoanodes. (1−5) The heart of these solar cells is a TiO 2 nanomaterial photoanode, which not only supplies a high internal surface area for dye sensitizer adherence but also acts as the stable medium for photogenerated electrons delivery. The effective combination of robust light scattering, substantial dye loading, and fast electron transport for the HTs nanostructures is responsible for the remarkable performance.ĭye-sensitized solar cells (DSCs) stand out as one of the promising “next generation” optoelectronic devices due to their simple production techniques, low manufacturing cost, and chemical stability. When the specifically created hierarchical TiO 2 was used as the photoanode in dye-sensitized solar cells (DSCs), a significantly improved power conversion efficiency (PCE) of 8.32% was achieved, outperforming a typical TiO 2 (P25) nanoparticle-based reference cell (η = 5.97%) under the same film thickness. In the course of the synthesis, spindle-like rutile TiO 2 and the intermediate anatase phase were first obtained through a dissolution/precipitation/recrystallization process, with the former serving as the substrates and the latter as the nucleation precursor to growing the branches, which finally gave birth to the production of 3D HTs nanostructures. This study presents a unique and straightforward room temperature-based wet-chemical technique for the self-seeding preparation of three-dimensional (3D) hierarchically branched rutile TiO 2, abbreviated HTs, employing titanate nanotubes as the precursor.
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