Transparent Conducting Films of Indium Tin Oxide with 3D Mesopore Architecture

Abstract

Transparent conducting oxides (TCOs) with a well-defined mesoporous framework are of considerable interest for applications in optoelectronic, electrochromic, and electroluminescent devices, solar cells, and sensors. It is the unique combination of transparency, high conductivity, well-defined 3D mesoporosity and high surface area that allows the incorporation of optoelectroactive species, facilitates electron transport to these centers, and efficiently harvests the electron-induced optical response or, vice versa, the photon-induced electron flow. These features would allow and facilitate the further development of dye-sensitized solar cells (DSSCs). However, such conducting transparent frameworks with nanometer-scale periodicity have not been accessible yet, being available solely as nonporous and macroporous layers or powders. [1][2][3] The generation of indium tin oxide (ITO) with well-ordered accessible mesoporosity and high conductivity has not been accomplished yet, partly because of the necessity of high crystallinity, which is indispensable for good electrical conductivity but inconsistent with organized 3D mesoporosity. Recently, the preparation of such mesoporous material was attempted by deposition of ITO onto porous glass substrates, providing composites with an inhomogeneous distribution of ITO. [4,5] Generally, sol-gel techniques are more advantageous for the preparation as they are applicable to various metal oxides and different types of substrates, require mild preparation conditions and, most importantly, allow the control of porosity by appropriate structure-directing agents such as self-organized surfactant micelles from block copolymers. Only a few template-assisted sol-gel syntheses using ITO have been reported, providing powders with quite high resistivity [6] or materials with irregular porosity resulting from the loose packing of crystallites. [7,8] Hence, subsequent functionalization of such material is significantly impeded. Mesoporous powders and macroporous films of undoped indium oxide were produced by sol-gel processes, but the resistivity of such material is usually too high for practical applications. [3,9] In general, the synthesis of films is aggravated by the rather poor ability of indium compounds to form stable sols and the difficulty in controlling the crystal growth of ITO. Using evaporation-induced self-assembly (EISA), various metal oxides (in particular, TiO 2[10]) have recently been obtained as crystalline thin films with ordered 3D mesoporosity. However, this technique has not been applied to certain metal oxides, particularly ITO, because of the breakdown of the mesostructure upon crystallization. The need of suitable block-copolymer templates was identified as one of the key features in the synthesis of mesoporous films with high crystallinity. [11] Owing to a new type of block copolymers with vastly improved structure-directing properties (poly(ethylene-co-butylene)-b-poly(ethylene oxides), referred to as "KLEs"), [12] we have overcome the collapse of the mesoscopi...

Dye‐Anchored Mesoporous Antimony‐Doped Tin Oxide Electrochemiluminescence Cell

“…So far, only mesoporous tin-doped indium oxide (meso-ITO) materials have been reported, but either their conductivity is very low due to low crystallinity [5] or their conductivity is reasonable but the mesostructure can only be templated with a specialty polymer surfactant. [6] …”

Kompostite auf Basis von Zeolithen oder geordnet mesoporösen Oxiden für Anwendungen in der Photonik und Sensorik

“…Der mittlere Oxidationszustand der Zinnoxid-Gastspezies nach der Reduktion mit Kohlenmonoxid und Wasserstoff und Re-Oxidation mit Sauerstoff konnte zusätzlich mittels In-situ- 119 Sn-Mößbauerspektroskopie bestimmt werden. Dabei stellte sich heraus, dass mittels H 2 reduzierte SnO 2 -Partikel in den Poren von Y-Zeolithen aufgrund der Bildung einer Schale aus metallischem Zinn um den Kern der Partikel nicht vollständig re-oxidiert werden kön-nen [47].…”

Periodically Ordered Meso‐ and Macroporous SiO2 Thin Films and Their Induced Electrochemical Activity as a Function of Pore Hierarchy

“…Such 2D-SAXS patterns are consistent with the templating behavior of "KLE" block copolymers described previously. [16][17][18][19] For this reason, 2D-SAXS patterns of the hierarchically structured pore systems were of particular interest. We find that cotemplating with "IL" (Fig.…”