Matteo Biancardo

A potential and ion switched molecular photonic logic gate

A molecular photonic logic gate is demonstrated by integrating electrical (potential) and chemical (ionic) switching functions into molecules attached at an externally addressable semiconductor substrate.

Analysis of charge transport in arrays of 28 kDa nanocrystal gold molecules

Arrays of 28 kDa nanocrystal gold molecules behave as weakly-coupled molecular solids comprising discrete nanoscale metallic islands separated by insulating ligand barriers. The key parameters which are found to dominate charge transport are (a) the single-electron nanocrystal charging energy, governed by the core diameter, the dielectric properties of the passivating ligands and classical electrostatic coupling between neighbouring cores; (b) the inter-nanocrystal tunnel barrier resistance that arises from the insulating nature of the ligand bilayers that separate the cores; and (c) the dimensionality of the network of current-carrying paths.

Large area polymer solar cells

The fabrication of very large area polymer based solar cell modules with a total aperture area of 1000 cm2 has been accomplished. The substrate was polyethyleneterephthalate (PET) foil with a pre-etched pattern of indium-tin-oxide (ITO) anodes. The module was constructed as a matrix of 91 devices comprising 7 rows connected in parallel with each row having 13 individual cells connected in series. The printing of the organic layer employed screen printing of a chlorobenzene solution of the active material that consisted of either poly-1,4-(2-methoxy-5-ethylhexyloxy) phenylenevinylene (MEH-PPV) on its own or a 1:1 mixture (w/w) of MEH-PPV and [6,6]-phenyl-C61-butanoic acid methyl ester (PCBM). Our first results employed e-beam evaporation of the aluminium cathode directly onto the active layer giving devices with very poor performance that was discouragingly lower than expected by about three orders of magnitude. We found that e-beam radiation leads to a much poorer performance and thermal evaporation of the aluminium using a basket heater improved these values by an order of magnitude in efficiency for the geometry ITO/MEH-PPV/C60/Al. Finally the lifetimes (τ1/2) of the modules were established and were found to improve significantly when a sublimed layer of C60 was included between the polymer and the aluminium electrode. Values for the half life of 150 hours were typically obtained. This short lifetime is linked to reaction between the reactive metal electrode (aluminium) and the constituents of the active layer.

Synthesis of conjugated polymers containing terpyridine metal complexes: application in organic solar cells

The synthesis of two new poly(dialkylstilbenevinylene)s obtained through a palladium-catalyzed polymerization with a controlled molecular weight and a terpyridine moiety in the backbone is presented. Assembly using ruthenium complexation led to coordination polymers with a ruthenium complex in the middle. The coordination homo and copolymers were characterized using NMR, UV-vis and were processed into thin films for solar cells applications. The best photoresponse was obtained for the device prepared from the ruthenium homopolymer bearing cyano substitutents with a maximum output power of 0.86 μW cm-2 and a fill factor of 26% under illumination at 1000 W m-2 AM1.5. A blend of this compound with a zinc porphyrin was also investigated and gave a lower performance.

A process-line for large area organic solar cells

In this paper we would like to address the key role of fabrication in the performance and lifetime of organic photovoltaics. The realization of a complete process line for the construction of large area organic photovoltaics (250 x 400 mm) is described. Among many of the factors that influence organic solar cell lifetime, oxygen and water exposure is the most important. Multiple processes have to be performed under controlled atmosphere and a glove box (or glove boxes), which involves more volume than commercially available glove boxes, needs to house different instruments. The processes housed in the glove boxes were spin coating, evaporation, lamination/sealing and testing, under an inert atmosphere. The main strategy employed multiply connected glove boxes with one load lock. The first glove box was used for spin coating and lamination/sealing, the second will house a screen printer and the third one accommodate an evaporator completely build in house. The evaporator has 2 thermal evaporation sources and 2 e-beams with 4 and 1 crucibles. The process line should allow the entire device realization from substrate coating, to electrode evaporation including the sealing process avoiding air and water exposure. Organic solar cells from small test cells on ITO glass to big modules (250 x 400 mm) of 91 connected cells on ITO PET substrates were fabricated and characterized.