Elena Dilonardo

Fluoro-functionalization of vinylene units in a polyarylenevinylene for polymer solar cells

A low band-gap copolymer PDTBTFV alternating bis-thienyl-(bis-alkoxy)-benzothiadiazole blocks with difluorovinylene units and its non-fluorinated counterpart PDTBTV have been synthesized and characterized as donor materials in bulk heterojunction (BHJ) solar cells with PCBM as the acceptor. The solar cells with the fluorinated polymer show better photovoltaic performances than those recorded with the non-fluorinated material. Comparative spectroscopic and computational studies, together with morphological, electrical and optical characterization of thin films, have been carried out to shed light on the reasons for the improvement of performances as induced by the double bond fluorination. Our study introduces the fluorinated double bond as a new conjugated unit in donor polymers for BHJ solar cells.

Plasma deposited Pt-containing hydrocarbon thin films as electrocatalysts for PEM fuel cell

High performance electrocatalytic hydrocarbon thin films containing Pt nano-clusters are deposited by simultaneous plasma polymerization of ethylene and sputtering of a Pt target. The proposed synthetic approach largely simplifies the PEMFC electrocatalyst fabrication process with respect to conventional methods. The deposition of the hydrocarbon matrix provides the mechanical support and electronic continuity, ensuring a uniform metal dispersion, avoiding Pt nanoparticle agglomeration. The Pt catalyst is dispersed as small vertically stacked clusters with size less than 10 nm in columnar thin (250–500 nm) films. PEMFC testing with plasma deposited 500 nm thick film and 0.513 mg cm−2 Pt load as anodic electrocatalyst led to a maximum reproducible power density as high as 300 mW cm−2.

Silicon doping effect on SF6/O2 plasma chemical texturing

A SF6/O2 plasma chemical etching is proposed as a process to texture n- and p-doped c-Si (100) by chemical reactivity of active fluorine species, under conditions avoiding ion bombardment and sputtering. Under this chemical etching regime, we found a strong impact of silicon doping on texturing characteristics and effectiveness. Specifically, an anisotropic square-based hillock-like texturing with 6% reflectivity is obtained for n-type Si. Conversely, for p-type Si, H2 plasma pretreatments are necessary to activate the silicon etching and obtain a nanotextured surface with a reflectivity of 16%. Reflectance from textured silicon surfaces is investigated and correlated to the morphology, surface roughness, and dimension of features.

Tailoring Optical Properties of Blue-Gap Poly(p-phenylene Vinylene)s for LEDs Applications

There has been growing interest in developing new semiconducting polymers for applications in optoelectronics (OLEDs) due to their exceptional processability and appealing characteristic of manipulating electronic and optical properties by tuning of molecular structure and self-assembling. This study is an investigation on the interplay among supermolecular organization and optical properties of thin films of the poly[2-(2-ethylhexyloxy)-5-methoxy]-1, 4-phenylenedifluorovinylene (MEH-PPDFV) conjugated polymer, which has fluorinated vinylene units. This interplay is elucidated exploiting atomic force microscopy, spectroscopy ellipsometry, photoluminescence and electroluminescence. Thin films of MEH-PPDFV have been deposited by drop casting on indium-tin-oxide (ITO), quartz and glass substrates. The dependence of polymer chains self-organization and morphology on substrate surface is presented. Furthermore, it is demonstrated that the presence of F-atoms in the vinylene units of the MEH-PPDFV yields a blue optical band gap with the maximum of the fundamental HOMO-LUMO transition at 331 nm and photoluminescence at 458 nm. The OLED built with the above polymer shows a very stable blue-greenish electroluminescence that is also achieved at 504 nm.