We present a general and in-depth study of the effect of dopants in hybrid inorganic/organic ZnO/PAA (polyacrylic acid) nanocomposites. These dopants vary as much by their ionic size, as by their electronic valence and some of them have been used in ZnO due to their known magnetic and/or optical properties. The chemical nature of the dopants controls their ability to incorporate into ZnO crystal lattice. Three concentrations (0.1%, 1% and 5%) of dopants were studied in order to compare the effect of the concentration with the results obtained previously in the literature. Our results confirm in the first place the trend observed in the literature, that increase in dopant concentration leads to quenching of visible luminescence for ZnO nanocrystals obtained by very different processes. However, the degradation of photoluminescence quantum yield (PL QY) is not inevitable in our nanocomposites. At low doping concentration for some dopants with a small or comparable ionic radius than Zn2+, PL QY can be maintained or even improved, making it possible to tune the visible emission spectrum between 2.17 eV and 2.46 eV. This opens up the prospect of synthesizing phosphors without rare earth for white LEDs, whose spectrum can be tuned to render warm or cold white light, by a chemical synthesis process with a low environmental impact.

Four series of dyes were studied theoretically and characterized by functional density theory (DFT) and time-density functional theory (TD / DFT) using the B3LYP method and the 6-31G base set (d, p ) to systematically explore the structure-property relationship of dyes with the D-π-A architecture and the performance of dye sensitized solar cells. These new compounds based on Thiophene and Oxathiazole bound to cyanoacrylic acid 2 as the acceptor and the electron donor unit has varied. The key parameters associated with the short circuit current density Jsc and the open circuit photovoltage Voc have been characterized and analyzed in detail. All assay results show that DM2 dye should be the best candidate to manufacture dye-based solar cells because of the better electronic property low energy gap and optimal optical absorption bung (wide absorption band of 300 to 900 nm for the adsorbed dye) in neutral and doping states and other exceptional parameters.

The market of White Light Emitting Diodes (WLEDs) has known a tremendous development in the recent years, due to the possibility of the reduction of the energy consumption when compared to fluorescent or incandescent lamps. The materials most commonly used as phosphors in these diodes are based on rare-earth elements. Knowing that 95 % of rare earth elements are produced by China, it becomes clear that it is necessary to develop rare earthfree phosphors for future WLEDs. High photoluminescent quantum yield (PLQY), thermally stable green/yellow/red emission and easy scale–up process are required for the industrial applications of such new phosphors. Zinc oxide is a potential candidate for the replacement of rare earth-based phosphors for the application in WLEDs. ZnO nanoparticles (NPs) have recently aroused a growing interest as down-shifting materials as they exhibit luminescence in the visible due to various intrinsic crystalline defects or surface defects after the absorption of the UV light. The photoluminescence, internal PL quantum efficiency, morphology and crystal structure of ZnO nanoparticles doped with various atoms (metallic or not), synthesized by the sol-gel method have been studied. We show that the luminescent and colorimetric characteristics of doped ZnO nanoparticles depend on the choice of the corresponding doping atom and the doping concentration. Prospects for using zinc oxide as a phosphor in WLEDs are discussed, together with their color rendering index (to control the color of the WLEDs emission), correlated color temperature and PLQY.

Intense visible nano-emitters are key objects for many technologies such as single photon source, bio-labels or energy convertors. Chalcogenide nanocrystals have ruled this domain for several decades. However, there is a demand for cheaper and less toxic materials. In this scheme, ZnO nanoparticles have appeared as potential candidates. At the nanoscale, they exhibit crystalline defects which can generate intense visible emission. However, even though photoluminescence quantum yields as high as 60% have been reported, it still remains to get quantum yield of that order of magnitude which remains stable over a long period. In this purpose, we present hybrid ZnO/polyacrylic acid (PAAH) nanocomposites, obtained from the hydrolysis of diethylzinc in presence of PAAH, exhibiting quantum yield systematically larger than 20%. By optimizing the nature and properties of the polymeric acid, the quantum yield is increased up to 70% and remains stable over months. This enhancement is explained by a model based on the hybrid type II heterostructure formed by ZnO/PAAH. The addition of PAAX (X = H or Na) during the hydrolysis of ZnEt2 represents a cost effective method to synthesize scalable amounts of highly luminescent ZnO/PAAX nanocomposites.

In this work, we present elaboration of Ta-based thin films by ALD from a novel tantalum precursor, the eta2-N,N'-isopropylethylguanidinato-tetra-diethylamino tantalum ([eta2-(i)PrNC(NEt2)NEt]Ta(NEt2)4, IEGTDEAT). Ammonia was used as reducing agents. The experimental conditions were optimized by quartz microgravimetry, studying the influence of duration of precursors and purge pulses and the substrate temperature. An optimal deposition temperature of 260 degrees C was showed. Ta-based thin films deposited on planar and patterned substrates showed a perfect conformality and continuity, even at low number of cycles.