Vertically-aligned CdTe nanowire (NWs) were grown for the first time by metalorganic vapor phase epitaxy, using diisopropyl-telluride and dimethylcadmium as precursors, and Au nanoparticles as metal catalysts. The NWs were grown between 485 and 515, °C on (111)B-GaAs substrates, the latter overgrown with a 2-μm thick CdTe epilayer. To favor the Au-catalyst assisted process against planar deposition of CdTe, an alternate precursors flow process was adopted during NW self-assembly. Field emission electron microscopy observations and X-ray energy dispersive analyses of CdTe NWs revealed the presence of Au-rich droplets at their tips, the contact-angle between Au-droplets and NWs being, ~130°. The NW height increases exponentially with the growth temperature, indicating that the Au-catalyzed process is kinetics-limited (activation energy: ~57, kcal/mol), but no tapering is observed. Low temperature cathodoluminescence spectra recorded from single NWs evidenced a band-edge emission typical of zincblend CdTe, and a dominant (defects-related) emission band at 1.539 eV.

In this work two different techniques to modify the polymeric surfaces are compared; Laser irradiation and ion implantation were performed on Ultra High Molecular Weight Polyethylene (UHMWPE) samples. The irradiation treatment was performed by using two different laser sources operating in the UV and IR range, applying many laser shots in air atmosphere on the polymer surface. Ion implantation was performed using a new LIS (Laser Ion Source) accelerator with an accelerating voltage of 40 kV. Contact angle, roughness and Fourier Transform Infra Red (FT-IR) measurements were performed on the samples before and after the two treatments in order to obtain information on the UHMWPE modification.

Copper (Cu) thin films were deposited on yttrium (Y) substrate by sputtering. During the deposition, a small central area of the Y substrate was shielded to avoid the film deposition and was successively used to study its photoemissive properties. This configuration has two advantages: the cathode presents (i) the quantum efficiency and the work function of Y and (ii) high electrical compatibility when inserted into the conventional radio-frequency gun built with Cu bulk. The photocathode was investigated by scanning electron microscopy to determine surface morphology. X-ray diffraction and atomic force microscopy studies were performed to compare the structure and surface properties of the deposited film. The measured electrical resistivity value of the Cu film was similar to that of high purity Cu bulk. Film to substrate adhesion was also evaluated using the Daimler-Benz Rockwell-C adhesion test method. Finally, the photoelectron performance in terms of quantum efficiency was obtained in a high vacuum photodiode cell before and after laser cleaning procedures. A comparison with the results obtained with a twin sample prepared by pulsed laser deposition is presented and discussed.

Simultaneous photoluminescence (PL) and external quantum efficiency (EQE) confocal mapping is used to investigate the correlation between the local PL and the EQE in a regioregular poly(3-exylthiophene):poly(9,9-dioctylfluorene-co-benzothiadiazole) inverted bulk heterojunction solar cell. We show that the charge generation and charge collection are strongly non-uniform on a length scale up to 100 μm. Our results evidence that organic solar cells optimization requires not only the control of the submicrometric active materials arrangement but also the control of the large scale device uniformity.

Different silver nanostructures have been rapidly synthesized under microwave irradiation from a solution of silver nitrate (AgNO3) and beta-D glucose; neither additional reducing nor capping agent were required in this soft green solution approach. Not only spherical nanoparticles, but also necklace and wires have been synthesized. The plasmon resonances of the synthesized silver nanostructures were tuned by varying the irradiation time and hence by changing size and morphology of nanostructures. The obtained nanostructures were characterized by X-Ray diffraction (XRD), Uv-Vis spectroscopy (Uv-Vis), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). The change of peak position and the shape of the absorption spectra were clearly observed during the whole reaction process; in fact, it was evidenced that initially Ag nanoparticles were formed, which, as reaction time elapsed, self-assembled and fused with each other to yield nanowires.

The efficiency optimization of bulk heterojunction solar cells requires the control of the local active materials arrangement in order to obtain the best compromise between efficient charge generation and charge collection. Here, we investigate the large scale (10–100 μm) inhomogeneity of the photoluminescence (PL) and the external quantum efficiency (EQE) in inverted all-polymer solar cells (APSC) with regioregular poly(3-hexylthiophene) (P3HT):poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) active blends. The morphology and the local active polymer mixing are changed by depositing the active layer from four different solvents and by thermal annealing. The simultaneous PL and EQE mapping allowed us to inspect the effects of local irregularities of active layer thickness, polymer mixing, polymer aggregation on the charge generation and collection efficiencies. In particular, we show that the increase of the solvent boiling point affects the EQE non-uniformity due to thickness fluctuations, the density non-uniformity of rrP3HT aggregate phase, and the blend components clustering. The thermal annealing leads to a general improvement of EQE and to an F8BT clustering in all the samples with locally decrease of the EQE. We estimate that the film uniformity optimization can lead to a total EQE improvement between 2.7 and 6.3 times.