No abstract

Bi-layer coatings from sputtered indium tin oxide (ITO) and gallium doped zinc oxide (Ga:ZnO) were investigated for transparency in the visible range of the electromagnetic spectrum, optical rejection ability in the near infrared spectrum and conductivity for the novel quantum dot-based solar cells. The multilayer stack produced at optimal oxygen partial pressure exhibits improved optical properties without worsening the electrical ones, even after additional oxidation during the reactive sputtering of the metal-oxides. With a mean optical transmittance of 91.3% in the visible region, mean optical rejection greater than 65% in the infrared range and resistivity lower than 0.4 × 10−2 Ω.cm, this coating is good candidate for front panel electrode in the CdS/ZnS core-shell quantum dot-based solar cells.

The aim of the study is the preparation and electrical characterization of lead-free ferroelectric oxide BaSrTiO3 in the composition with a piezoelectric polymer. The properties of the deposited films were compared with pristine oxide. Atomic force microscopy showed a smooth surface, and a regular and homogeneous distribution of particles of both components in the composite films. The dielectric properties (electric permittivity and dielectric loss) were investigated at different temperatures ranging from 5 to 130 °C. Impedance spectroscopy was applied in the frequency range 100–100 kHz. The dielectric constant increase with the addition of a piezoelectric polymer to the ceramic phase was demonstrated. It can be seen that the interface conditions at the electrodes are improved after inserting a piezoelectric polymer. The interpretation of the plots of the complex impedance vs. frequency, and the real part of the impedance vs. the imaginary part, give information about the polarization process revealed in the structures.

Nanowires of ferroelectric potassium niobate were grown by filling nanoporous templates of both side opened anodic aluminum oxide (AAO) through radiofrequency vacuum sputtering for multisensor fabrication. The precise geometrical ordering of the AAO matrix led to well defined single axis oriented wire-shaped material inside the pores. The sensing abilities of the samples were studied and analyzed in terms of piezoelectric and pyroelectric response and the results were compared for different length of the nanopores (nanotubes)—1.3 µm, 6.3 µm and 10 µm. Based on scanning electronic microscopy, elemental and microstructural analyses, as well as electrical measurements at bending and heating, the overall sensing performance of the devices was estimated. It was found that the produced membrane type elements, consisting potassium niobate grown in AAO template exhibited excellent piezoelectric response due to the increased specific area as compared to non-structured films, and could be further enhanced with the nanowires length. The piezoelectric voltage increased linearly with 16 mV per micrometer of nanowire’s length. At the same time the pyroelectric voltage was found to be less sensitive to the nanowires length, changing its value at 400 nV/µm. This paper provides a simple and low-cost approach for nanostructuring ferroelectric oxides with multisensing application, and serves as a base for further optimization of template based nanostructured devices.

Two layer system from sputtered indium tin oxide (ITO) and gallium doped zinc oxide (Ga:ZnO, GZO) were studied for transparency in the visible electromagnetic range, reflectivity in the near infrared range, conductivity and valent band for a solar cells with quantum dots. The bi-layer coatings produced at optimized oxygen partial pressure, films thickness and surface roughness exhibit improved optical properties without worsening the electrical parameters, even if additional oxygen introduction during the reactive sputtering of the GZO. With an average optical transmittance of 91.3% in the visible range, average reflection and resistivity lower than 0.4 × 10−2 Ω.cm, these coatings are suitable for top electrode in the solar cells. The obtained results reveal that multilayered stacks of transparent ITO/Ga-doped ZnO coatings possess relatively low surface roughness (7–9 nm) and appropriate refractive index. The additional oxidation of GZO films induces modification of the film thickness and respectively of their optical performances.