Electrospun antimony doped tin oxide (ATO) nanofibers as a versatile conducting matrix

Abstract

Nanoparticles of ATO (antimony doped tin oxide) were used to produce thick conductive, free standing mats of nanofibers via electrospinning. These fibrous mats were incorporated into polymer films to produce a transparent conducting polymer foil. Moreover, the fiber mats can serve as porous electrodes for electrodeposition of Prussian Blue and TiO 2 and were tested in dye-sensitized solar cells.TCO (transparent conducting oxide) materials are widely used in opto-electronic applications as transparent electrodes, commonly as thin, compact films deposited on glass or quartz substrates.1,2 These TCO layers of 200-300 nm thickness possess sheet resistances typically below 20 O/& and transparencies above 85% in the visible range, making them also suitable as two-dimensional electrodes for electrochromic devices 3 and solar cells.4 TCO films with 3D porosity with pore sizes beyond 100 nm are supposed to be useful for diverse applications. As proposed by Zaban et al., a 3D TCO electrode theoretically offers advantages for electron collection in DSSCs (dye-sensitized solar cells), 5 due to a higher surface area and a shorter electron diffusion pathway to the back electrode. The practical realization of such DSSCs with TiO 2 on ITO (indium tin oxide) nanopowders 6 and nanowires generated by laser-ablation 7 showed only low conversion efficiency, but recently a more elaborate approach based on a poly(carbonate) template yielded around 4% efficiency. 8 In addition, porous TCO electrodes might prove suitable in other applications with non-conducting polymers or oxides with low intrinsic conductivities, as for example oxide cathodes for Li-batteries. Here we demonstrate a novel procedure allowing the production of ATO (antimony doped tin oxide) nanofiber mats and their usage to endow intrinsically insulating polymer films with conductivity, and as highly porous electrodes for electrodeposition and device fabrication. To the best of our knowledge, this is the first working example of a nanofiber-based ATO electrode. For ordinary TCO electrodes, typical deposition techniques are CVD and PVD (chemical and physical vapor deposition), including spray pyrolysis, PLD (pulsed laser deposition) and magnetron sputtering, resulting in compact layers. Various attempts have been made to employ sol-gel processing, yielding good transparency, but generally much lower conductivity. Main benefits of sol-gel approaches are the possibility of solution-based coating technology and the facile generation of porosity through suitable polymer templates, as demonstrated for mesoporous and macroporous ITO.10,11 An alternative concept to endow TCOs with porosity is the generation of nanofibers by electrospinning. The combination of a suitable polymer as a carrier with conventional sol-gel processing thus can be applied for the electrospinning of metal oxide fibers, including ITO. 8,15 However, for other n-type TCO materials like ATO, FTO (fluorine doped tin oxide) or AZO (aluminum doped zinc oxide) only low conductivities have been reported, even for ...

Highly Interconnected Macroporous and Transparent Indium Tin Oxide Electrode

“…Ostermann et al . worked on similar material, antimony tin oxide, and because of those difficulties, they concluded that it was impossible to obtain continuous oxide nanofibrous layers of significant thickness by direct deposition on the solid substrate, due to inevitable breaking of fibers and delamination of the layer . For that reason, some of the early reports, as well as all of the later applications of ITO nanofibers have been performed using free‐standing mats ,.…”

Porous and Transparent Metal‐oxide Electrodes : Preparation Methods and Electroanalytical Application Prospects

“…The procedure could be optimized for better transparency but at the cost of a higher sheet resistance (Figure ). A lower sheet resistance of 400 Ω sq −1 for ATO was obtained by depositing porous layers in the form of free‐standing mats and using ATO nanoparticles as precursors . Similarly, AZO nanofibers have been prepared and it was found that the grain size becomes lower with rising Al doping levels .…”

From Bare Metal Powders to Colloidally Stable TCO Dispersions and Transparent Nanoporous Conducting Metal Oxide Thin Films

“…The herein reported TCO NPs possess diameters of 3–6 nm, are colloidally stable, can be produced on a multi‐gram scale and are well‐suited for spin‐coating nanoporous, transparent, and conductive TCO thin films7 (see Scheme ) with potential utility in lithium ion batteries, solar and photo‐electrochemical cells, electrochromics and sensors, flat‐panel displays, transparent thin‐film transistors, optoelectronic devices, and photonic crystal architectures 8–12. Additionally, such TCO dispersions can potentially be ink‐jet printed4, 13 or electrospun into TCO nanofibers 14…”