Hierarchical Twin-Scale Inverse Opal TiO₂ Electrodes for Dye-Sensitized Solar Cells

Abstract

We describe the preparation of three-dimensional hierarchical twin-scale inverse opal (ts-IO) electrodes for dye-sensitized solar cells (DSSCs). The ts-IO TiO(2) structure was obtained from a template fabricated via the assembly of mesoscale colloidal particles (40-80 nm in diameter) in the confined geometry of a macroporous IO structure. The photovoltaic properties of ts-IO electrodes were optimized by varying the layer thickness or the size of mesopores in the mesoscale colloidal assembly. Electron transport was investigated using impedance spectroscopy. The result showed that due to the competing effects of recombination and dye adsorption, the maximum efficiency was observed at an electrode thickness of 12 μm. The electrodes of smaller mesopores diameters yielded the higher photocurrent density due to the decrease in the electron transport resistance at the TiO(2)/dye interface. A maximum efficiency of 6.90% was obtained using an electrode 12 μm thick and a mesopore diameter of 35 nm.

A colloidoscope of colloid-based porous materials and their uses

“…467 This additional absorption can improve the efficiency. For example, it accounted for a >50% increase in the efficiency of a DSSC, 447 and can be seen clearly in Figure 30 for a photoanode made from WO 3 , where the efficiency varies as a function of wavelength depending on the periodicity of the structure. 393 There is a clear efficiency enhancement for the structure made with 200 nm colloids, which has a photonic bandgap overlapping with the electronic absorption of WO 3 .…”

Vapor-phase hydrothermal synthesis of rutile TiO2 nanostructured film with exposed pyramid-shaped (1 1 1) surface and superiorly photoelectrocatalytic performance

“…Owing to excellent photocatalytic activity, titanium dioxide (TiO 2 ) has been widely investigated in varieties of applied fields such as environmental remediation, solar-driven hydrogen production, solar cells and lithium-ion batteries [1][2][3][4][5][6][7][8][9][10]. Although rutile TiO 2 possesses better chemical stability and UV absorption capability, anatase TiO 2 is more active for photocatalytic reaction than rutile TiO 2 ascribing to the more negative conduction band edge potential of anatase TiO 2 , which is more favorable for reducing O 2 to O 2 ÅÀ , greatly decreasing the recombination of photogenerated carriers [11][12][13][14].…”

Nanocrystalline Precursors for the Co‐Assembly of Crack‐Free Metal Oxide Inverse Opals

“…Additionally, fundamental questions related to photonic‐enhanced photocatalysis and band‐edge lasing could be investigated with defect‐free IO films. However, the formation of such metal oxide IOs remains a challenge in part due to the amorphous‐to‐crystalline phase transition and associated crystallization‐induced volume shrinkage of solid matrix during the heat treatment, whether purely crystalline precursors, amorphous sol–gel precursors, or a combination of both are used. Metal oxide sol–gel precursors present the additional challenge of high hydrolytic instability …”

“…Having both components allows the precursor to accommodate stresses during the self‐assembly process and to minimize volume changes during phase transitions, leading to high‐quality inverse opal films: the crystalline phase suppresses crack formation during calcination, and the hydrated amorphous phase suppresses crack formation during the drying stage. It is noteworthy that neither the assembly of purely crystalline precursor phase nor the use of sol–gel amorphous precursors nor a simple combination of both allows for the formation of such ordered, defect‐free crystalline metal oxide films. These crack‐free IOs enable or enhance a range of applications, such as photocatalysis and band‐edge lasing .…”