Hierarchically structured aggregates, consisting of TiO₂ nanoparticles were produced via one-step solvothermal syntheses with a mixed solvent system containing both acetic acid and ethanol. Two of the resulting structures, one ~700 nm and the other ~300 nm in diameter, were found to be comprised of 8.5 nm and 10.5 nm anatase crystals, and possess specific surface areas of 138 and 106 m² g⁻¹ respectively. These particles were incorporated into Dye-sensitized Solar Cells (DSCs) as high surface area scattering layers, along with a layer of a transparent material. Solar-to-electric conversion efficiencies (PCE) of 9.1% and 8.2% were recorded using these aggregated particles as compared to those of commonly used large particles scattering layer 7.4%.

P25 is one of the most widely used forms of titanium(iv) oxide (TiO₂), routinely utilised in dye-sensitised solar cells (DSCs), where it is often employed as a control, in spite of its poorly defined nature and the typically low device efficiency.

Many researchers working on the development of dye-sensitized solar cells (DSCs) continue to focus on the synthesis of photoanode materials with high surface area, along with high light scattering ability to enhance light harvesting efficiency (LHE). Meanwhile, dye packing density, which also impacts the LHE significantly, is often overlooked. Solvothermally synthesized anatase TiO₂ nanoparticles (SANP) were obtained by a new and simple approach using a mixed solvent, ethanol and acetic acid. SANP were applied in photoanodes of DSCs using either metal-free organic dye (D149) or organometallic (N719) dyes. Dye loading (packing density) was correlated with the isoelectric point (IEP) in addition to light scattering effects were shown to determine the devices photovoltaic efficiency (PCE); specifically when compared with ones employing commercially available TiO₂ nanoparticles. SANP photoanodes sensitized with D149 dye were found to be optimised at 10 µm, yielding a PCE of 6.9%, superior to for transparent or transparent + scattering films from the commercial source (5.6% and 5.9%, respectively). Furthermore, a 7.7% PCE was achieved using a SANP photoanode sensitized with N719 dye, with 7.2% seen for the transparent photoanode and 7.9% with a scattering layer. The high PCEs of of SANP devices are attributed to the high dye loading capability in addition to light scattering. A further point of interest is that even with the increased reactivity of the surface towards dye adsorption, we did not observe any significant increase in recombination with the redox mediator, presumably due to the increased dye loading providing better shielding.

Ultraviolet (UV) radiation causes serious health risks. Inorganic metal oxides, such as titanium dioxide (TiO₂) and zinc oxide (ZnO), have long been recognized for their effectiveness as UV radiation filters/blockers in sunscreen formulations. TiO₂ and ZnO as UV-blocking materials have some limitations and issues such as producing harmful radicals and toxicity, respectively. As a result, there is a growing need to develop efficient and safe UV-blocking materials to overcome these limitations associated with the conventional TiO₂ and ZnO materials. Zinc stannate (Zn₂SnO₄), as a ternary metal oxide, is expected to be a promising candidate due to its optical properties and potential for UV-blocking capability. This study presents a comprehensive investigation into the development and characterization of Zn₂SnO₄ as a potential alternative UV filter to TiO₂ and ZnO. The fundamental characteristics, including structural, optical, and photocatalytic characteristics, as well as cell viability, were investigated for two Zn₂SnO₄ morphologies: cubic aggregate Zn₂SnO₄ nanoparticles (ZTO CANP) and Zn₂SnO₄ nanoparticles (ZTO NP), which were compared with the performance of TiO₂ nanoparticles (TiO₂ NP) and ZnO nanoparticles (ZnO NP). Interestingly, in addition to their promising UVB and partial UVA blocking properties, ZTO CANP and ZTO NP were found to be relativity photocatalytically inactive materials, which means they produce less free radical species as in the case of TiO₂ NP, and they cannot be considered as toxic materials as in the case of ZnO NP. To the best of our knowledge, this is the first direct comparison study examining the performance of Zn₂SnO₄ ternary metal oxide for its potential use as a UV filter. Further research and optimization need to be conducted on these materials, particularly on ZTO CANP as a promising alternative UV filter.