Ellipsoidal TiO₂ Hierarchitectures with Enhanced Photovoltaic Performance

Abstract

Hierarchical TiO(2) ellipsoids 250-500 nm in size have been synthesized on a large scale by a template-free hydrothermal route. The submicrometer-sized hierarchitectures are assembled from highly crystallized anatase nanorods about 17 nm in diameter with macroporous cavities on the outer shells. Based on the time-dependent morphological evolution under hydrothermal conditions, an oriented attachment process is proposed to explain formation of the hierarchical structures. Such hierarchical TiO(2) not only adsorbs large amounts of dye molecules due to high surface area, but also shows good light scattering caused by the submicrometer size. The TiO(2) hierarchitectures were deposited on top of a transparent TiO(2) nanocrystalline main layer to construct a double-layered photoanode for dye-sensitized solar cell (DSC) application, exhibiting enhanced light harvesting and power-conversion efficiency compared to a commercial TiO(2)-based electrode.

The Use of Rutile‐ and Anatase‐Titania Layers towards Back Light Scattering in Dye‐Sensitized Solar Cells

“…All the sensitized films exhibit an intense band around 540 nm ascribed to the typical lowest‐lying 1 MLCT Ru→dcbH absorption band of the N3 dye. The photoanode based on top microsphere scattering layers show higher overall absorptions, in particular for NCT/RMT with the highest amounts of dye uptake and light absorption . Worth of note, the lower dye uptake for the NCT photoanode – even NCT having the highest surface area – is because NCT films are thinner, with a lower final area for dye adsorption (NCT films are obtained in only two screen‐printing depositions, with 8 μm final thickness, while bilayered NCT/RMT or NCT/AMT films are fabricated in three depositions, with 12 μm final thickness).…”

“…However, the high transparency and negligible light scattering ability of such electrodes usually result in loss (non‐harvesting) of near infra‐red photons, hardly absorbed by the sensitizer layer ,. Extensive work has been dedicated to boost the power conversion efficiency by developing new photoanode architectures that can integrate both the benefits of high internal surface area and sufficient light scattering in a single morphology ,…”

Single-Layer TiO2 Film Composed of Mesoporous Spheres for High-Efficiency and Stable Dye-Sensitized Solar Cells

“…Recently, various hierarchical TiO 2 nanostructures, such as mesoporous spheres, − hollow spheres, − hierarchical flowers, , ellipsoids, and aggregates, have been synthesized and employed as photoanodes for efficient DSCs. Among them, mesoporous microspheres as photoanodes have been demonstrated to possess efficient dye loading and high light-harvesting ability owing to their high specific surface area and strong light scattering by combining the merits of primary nanocrystal building blocks and submicrometer-sized assembles.…”

Synergistic assembly of nanoparticle aggregates and texture nanosheets into hierarchical TiO2 core–shell structures for enhanced light harvesting in dye-sensitized solar cells

“…To resolve this dilemma, many groups are motivated to develop hierarchical TiO 2 micro-nanostructures, such as mesoporous beads, nano-embossed hollow spheres, hierarchical ellipsoids, spherical voids, and spherical nanoparticle aggregates, which can simultaneously provide light scattering and large surface area properties. [7][8][9][10][11][12][13][14][15] To obtain a much bigger surface area, the synthetic strategies for such purpose-built hierarchical TiO 2 micro-nanostructures usually have involved a combination of two or more independent procedures. For example, Caruso et al have prepared mesoporous TiO 2 beads through a combination of sol-gel and solvothermal process.…”