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LL9.03 - Nanostructured Ta-Doped TiO as a Highly Conducting Transparent Electrode/Functional Photoanode 
April 23, 2014   4:15pm - 4:30pm

The field concerning transparent conducting oxides (TCO) has recently been attracting much attention in the research for an alternative material to indium tin oxide (ITO) and for the development of oxide nanostructures in order to reach new functional properties not intrinsically present in the compact form of the TCO (e.g. advanced light trapping, large surface area, highly directional conductivity). We here present a study on Ta doped TiO (TaTO), belonging to a promising new class of TCOs recently discovered [1, 2].TaTO nanostructured thin films were deposited on soda lime glass substrates via nanosecond Pulsed Laser Deposition (PLD). The deposition process is performed at room temperature and then followed by a vacuum annealing (p < 4x10 Pa) to obtain single phase polycrystalline anatase. We investigated the effect of oxygen partial pressure during film synthesis and we were able to obtain compact (1-2.25 Pa range) and nanoporous-nanostructured (5-15 Pa range) thin films with a tree-like architecture. The role of the annealing temperature, time and cooling rate was analyzed in terms of structure, morphology and optoelectronic properties on both compact and nanoporous structures. The best electrical properties were obtained for deposition in oxygen pressure of 1.25 Pa coupled with a vacuum annealing at 550°C for 1 hour. The resistivity obtained for a 150 nm TaTO film is 5.9x10 Ωcm, with a mean transmittance in the visible range of 76.5%. As a matter of fact, this values are strongly competitive with the best results of the most studied Nb doped TiO. Moreover we have investigated the possibility to characterize the transport properties of the single tree-like nanostructures of TaTO by Scanning Photo Electron Microscopy with synchrotron radiation [3]. Preliminary results indicate an effective resistivity for the individual nano-structures lower than 10 Ωcm.Exploiting a variation of the oxygen background pressure during the deposition process we are able to realize a fully TiO-based hierarchically grown TCO-photoanode (compact + porous TaTO double layer), that we aim to test in dye sensitized/hybrid solar cells. Using such approach we want to combine the low resistivity of the compact TaTO bottom layer and the high surface area, light scattering properties and directional conductivity of the top layer tree-like architecture. Moreover we show how the transmittance of the double layered structure can be enhanced with respect to the single compact layer.1. Furubayashi, Y. Appl. Phys. Lett., 2005. 86(25): p. 252101.2. Hitosugi, T. Jpn. J. Appl. Phys. Part 2-Letters & Express Letters, 2005. 44(33-36): p. L1063-L1065.3. Jabeen, F. Nano Research, 2010. 3(10): p. 706-713.

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Keynote Address
Panel Discussion - Different Approaches to Commercializing Materials Research
Business Challenges to Starting a Materials-Based Company
Fred Kavli Distinguished Lectureship in Nanoscience
Application of In-situ X-ray Absorption, Emission and Powder Diffraction Studies in Nanomaterials Research - From the Design of an In-situ Experiment to Data Analysis