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In this work, the ZnO thin film, the Al-doped ZnO (AZO) thin film (0.98M ZnO, 0.02M Al) and the (Al,Co) co-doped ZnO thin film (AZO:Co) (0.95M ZnO, 0.02M Al, 0.03M Co) were deposited on the glass substrate by the Sol–Gel method. We fabricated a sample of the ZnO thin film, a sample of the AZO thin film and three samples of AZO:Co thin films. The spin-coating was used to deposit thin film on the glass substrate. The ZnO and the AZO thin films were annealed at 450${}^{\circ }$C while three samples of the AZO:Co thin films were annealed at 300${}^{\circ }$C, 450${}^{\circ }$C and 600${}^{\circ }$C in air for 60 min, respectively. In order to prepare three samples of the AZO:Co thin films, we deposited the (Al,Co) co-doped ZnO on the glass substrate for 20 s then all samples were per-heated at 80${}^{\circ }$C for 10 min. we repeated this deposition process five times for each sample. Finally, three samples were annealed at 300${}^{\circ }$C, 450${}^{\circ }$C and 600${}^{\circ }$C in air for 60 min, respectively. The procedure to prepare of the ZnO and AZO thin films was like the AZO:Co thin films except that the annealing temperature was 450${}^{\circ }$C. The structural and optical properties of the thin films were investigated by X-ray diffraction technique, UV-Vis spectrophotometer and Field Emission Scanning Electron Microscopy (FESEM). Results indicated that (Al,Co) co-doping in the ZnO thin film improve the optical transmission while changes in the lattice structure is small with respect to the AZO thin film. Also, the AZO:Co thin film which was annealed at 450${}^{\circ }$C exhibited simultaneously the high thickness and high optical transmission.

Al₂O₃-doped zinc oxide (in AZO, the Al₂O₃ contents are approximately 2 wt.%) films have been grown by radio frequency (RF) magnetron sputtering at room temperature under varied sputtering pressures ranging from 3.5–15 mTorr. The electrical resistivity of AZO films is about 2.22×10^-3 Ωcm (sheet resistance ~ 89 Ω/square for a thickness ~ 250 nm), and the visible range transmittance is about 80% at the argon sputtering pressure of 15 mTorr and a RF power of 100 W. This study analyzes the structural, morphological, electrical and optical properties of AZO thin films grown on soda-lime glass substrate with 2, 5, and 10 nm thick Al buffer layers (and SiO₂ buffer). For the films deposited on the 2 nm thick Al buffer layer, we obtained a c-axis-oriented AZO/Al thin film on glass with the XRD full-width at half maximum (FWHM) of 0.31 and root mean square (RMS) surface roughness of about 3.22 nm. The lowest resistivity of 9.46×10^-4 Ωcm (sheet resistance ~ 37.87 Ω/square for a thickness ~ 250 nm) and a high transmittance (80%) were obtained by applying a 2 nm thick Al buffer layer. In contrast, the resistivity was slightly increased by applying the SiO₂ buffer layer.

The composite of a nanocrystalline SnO₂ thick film deposited on an Al-doped ZnO ceramic substrate was firstly proposed. This study also provided a simple, fast and cost effective method to prepare SnO₂ thick film and Al-doped ZnO ceramic as well as the final composite. The crystal structure, morphology, composition, pore size distribution and gas sensitivity of the composite were investigated by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, Barrett–Joyner–Halenda analysis and gas sensitive measurement system. Results indicated that the composite was fully porous consisted of SnO₂, ZnO and ZnAl₂O₄ crystal phases. The macrosized pores generated in the composite could enhance the gas infiltration into the sensing layers effectively. In this way, combining a high gas-transporting-capability and a nanocrystalline SnO₂ thick film, the composite showed very impressive performance. The gas sensitivity of the composite was high enough for ethanol vapor with different concentrations, which was comparable to other kinds of reported SnO₂ gas sensors, while showing two straight lines with a turning point at 1000ppm. Finally, the gas sensitive mechanism was proposed based on the microstructure and composition of the composite.

In this work we investigate the effect of metal layer in the Al-doped ZnO (AZO)/Al/AZO structure. AZO and Al thin films are deposed successively at room temperature using DC magnetron sputtering by rotating the substrate holder without breaking the vacuum. The optical characterization of AZO/Al/AZO structure was performed by the spectroscopic ellipsometry under different incidence angles (55${}^{\circ }$, 65${}^{\circ }$ and 75${}^{\circ }$). For the AZO monolayer structure, it was found that the complex refractive index and the complex permittivity coefficient varied differently according to the incidence angle. The addition of Al layer (5nm thicknesses) in this monostructure reduces significantly this influence on the measurement, homogenizes the real refractive index variation and significantly reduces the real electrical coefficient permittivity in the visible range. In addition, the obtained depolarization values confirm the results of the AFM roughness revealing that the Al layer addition makes the surface smoother so that it meets the required conditions as the bottom electrode of organic light emitting diodes. The photoluminescence (PL) measurements indicate that the Al layer alters the PL emission. Actually, the Al layer enhances subsequently the PL emission and promotes the blue and red emission.

Presented in this paper is the result of a study on the utilization of Al-doped ZnO (AZO) and Ti-doped ZnO (TiZO) as a blocking layer (BL) in Dye-Sensitized Solar Cells (DSSCs). The DSSCs structure was FTO/BL/TiO₂/dye/electrolyte/Pt on FTO. The crystallinity and crystallite size of those BLs were shown to be affected by the dopant type and its concentration. From the photovoltaic characteristics of those DSSCs, the TiZO layer showed better contribution in enhancing the open voltage as a BL in comparison to the AZO. The effect of these layers on the solar cell characteristics in the fabricated DSSCs was found to be not merely due to the difference in their Ohmic resistance. There is also the contribution of back recombination kinetics from the photoexcited electrons via the dopant states in the AZO and TiZO layers, which are different among the layers due to the difference in dopant states distributions below their conduction bands.

Zinc oxide (ZnO) nanoparticles were synthesized by a simple solution route method using zinc acetate as the precursor and ethanol as the solvent. At a temperature of 60${}^{\circ }$C, a clear homogenous solution is heated to 100${}^{\circ }$C for ethanol evaporation. Then the obtained precursor powder is annealed at 600${}^{\circ }$C for the formation of ZnO nanocrystalline structure. Doped ZnO particle is also prepared by using aluminum nitrate nonahydrate to produce aluminum (Al)-doped nanoparticles using the same solution route method followed by annealing. Thin film fabrication is done by air evaporation method using the polymer polyvinyl alcohol (PVA). To analyze the optical and thermal properties for undoped and doped ZnO nanocrystalline thin film by precursor annealing, characterizations such as UV, FTIR, AFM, TGA/DTA, XRD, EDAX and Photoluminescence (PL) were also taken. It was evident that precursor annealing had great influence on thermal and optical properties of thin films while ZnO and AZO film showed low crystallinity and intensity than in the powder form. TGA/DTA suggests pre-annealing effect improves the thermal stability, which ensures that Al ZnO nanoparticle can withstand at high temperature too which is the crucial advantage in the semiconductor devices. UV spectroscopy confirmed the presence of ZnO nanoparticles in the thin film by an absorbance peak observed at 359nm with an energy bandgap of 3.4eV. A peak obtained at 301nm with an energy bandgap of 4.12eV shows a blue shift due to the presence of Al-doped ZnO nanoparticles. Both ZnO and AZO bandgap increased due to precursor annealing. In this research, PL spectrum is also studied in order to determine the optical property of the nanoparticle embedded thin film. From PL spectrum, it is observed that the intensity of the doped ZnO is much more enhanced as the dopant concentration is increased to 1wt.% and 2wt.% of Al in ZnO.