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Transparent conductive oxide (TCO) layers, to be implemented in photo-anodes for dye-sensitized solar cells (DSCs), were prepared by co-deposition of ZnO and Al using pulsed-direct current (DC)-magnetron reactive sputtering processes. The films were deposited at low deposition temperatures (R T-188 C) and at fixed working pressure (1.4 Pa) using soft power loading conditions to avoid intrinsic extra-heating. To compensate the layer stoichiometry, O 2 was selectively injected close to the sample in a small percentage (Ar: O 2= 69 sccm: 2 sccm). We expressly applied the deposition temperature as a controlling parameter to tune the incorporation of the Al 3+ species in the targeted position inside the ZnO lattice. With this method, Aluminum-doped Zinc Oxide films (ZnO: Al) were grown following the typical wurtzite structure, as demonstrated by X-ray Diffraction analyses. A combination of micro-Raman, X-ray photoelectron spectroscopy (XPS) and spectroscopic ellipsometry (SE) analyses has shown that the incorporated host-atoms are Al 3+ species in Zn 2+ substitutional position; their amount increases following a direct monotonic trend with the deposition temperature. Correspondently, the c-axis strain into the layer decreases due to the progressive ordering of the lattice structure and reducing clustering phenomena. The maximum average Al content inside the film was~ 2%, as measured by energy dispersive X-ray (EDX) spectroscopy, with a uniform distribution of the dopant species along the layer thickness traced by depth-profile XPS analyses. The optimised ZnO: Al layer, deposited at a rate of~ 7 nm/min, exhibits high transmittance in …
Multidisciplinary Digital Publishing Institute
Publication date: 
1 Jun 2016

Salvatore Sanzaro, Antonino La Magna, Emanuele Smecca, Giovanni Mannino, Giovanna Pellegrino, Enza Fazio, Fortunato Neri, Alessandra Alberti

Biblio References: 
Volume: 9 Issue: 6 Pages: 433