Publications by Libero Zuppiroli

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We have built a model organic field-effect transistor that is basically composed of a single layer of pentacene crystal in interaction with an oxide surface. Drain and source contacts are ohmic so that the pentacene layer can carry a current density as hig ...

We report on a study of pentacene thin-films grown by high vacuum deposition on silicon dioxide, using atomic force microscopy (AFM) and transmission electron microscopy (TEM). The nucleation density of pentacene islands on SiO2is found to rise as the deposition rate is increased but decreases at higher substrate temperature. This observation is consistent with the predictions of the rate-equation formalism for homogeneous nucleation. Hence, by controlling the two deposition parameters we are abl

We present a comparative study of the nucleation and growth of pentacene monolayer islands in the submonolayer regime onto inorganic substrates of SiO2 and sapphire (Al2O3) and organic substrates of poly(methyl-metacrylate) ...

We present the first thermoelectric measurements on pentacene field effect transistors. We report high values of the Seebeck coefficient at room temperature between 240 and 500 micro V/K depending on the dielectric surface treatment. These values are indep ...

Organic fluorescent molecules are infiltrated in the channels of zeolite L nanocrystals, thus creating organic-inorganic fluorescent nanoparticles. Combined with dielectric matrices, these fluorescent nanopigments open the way to the realization of novel o ...

By using pyran-containing donor-acceptor dyes as doping molecules in organic light-emitting devices (OLEDs), we scrutinize the effects of charge trapping and polarization induced by the guest molecules in the electro-active host material. Laser dyes 4-(dic ...

Electrically Detected Magnetic Resonance (EDMR) was used to investigate the influence of dye doping on spin-dependent exciton formation in aluminum (III) 8-hydroxyquinoline (Alq(3)) based Organic Light Emitting Diodes (OLEDs) with different device structur ...

In this work we propose a phenomenological microscopic approach to deal with pseudoinductive charge-relaxation processes (named also as negative capacitance phenomena) in organic molecules (tris-8-hydroxyquinoline-aluminum) and polymeric [poly(2-metoxy-5-( ...

In the last few years, an intense research effort has focused on the synthesis of fluorescent nanopigments for functional inks, light harvesting, tagging, tracing, (bio)labeling, imaging, and lighting applications. Moreover, combined with dielectric matric ...

We present a three-dimensional multiparticle Monte Carlo (3DMPMC) simulation of hopping transport in disordered organic molecular media. We used this approach in order to study the charge transport across an energetically disordered organic molecular heter ...

A novel, highly blue luminescent molecule containing donor and acceptor groups, 4,4 prime -di-(2-(2,5-dimethoxyphenyl)ethenyl)-2,2 prime -bipyridine, that shows photoluminescence emission at 450 nm with 43% quantum yield is designed and synthesized. Time d ...

We have used electrically detected magnetic resonance (EDMR) to study the spin dependent processes on the operation of diodes based on poly(2-metoxy-5-(2'-etil-hexiloxy)-1,4-phenylene vinylene) (MEH-PPV) and on tris-8-hydroxyquinoline-aluminum (Alq3). In MEH-PPV based diodes, the EDMR signal is found to be composed of two lines, a Lorentzian with ΔHpp=5 G and a Gaussian with ΔHpp=24 G. The g-factor of both components is about 2.0022. The signal is quenching, typi

A charge carrier in the channel of an organic field-effect transistor (OFET) is coupled to the electric polarization of the gate in the form of a surface Fröhlich polaron [N. Kirova and M. N. Bussac, Phys. Rev. B 68, 235312 (2003)]. We study the effects of ...

The charge carrier mobility in the transport channel of an organic transistor is estimated within the framework of a trap-and-release model. The model accounts for the observed dependence of the mobility on the dielectric constant "epsilon" of the gate ins ...

The remarkable effect on lifetime improvement of copper phthalocianine (CuPc) coated indium tin oxide (ITO) anode of organic light emitting diodes (OLED's) is experimentally well approved. Also known are the electrode morphology, with and without CuPc coating, the energy levels of the used materials, important for charge injection and conduction, the carrier mobility etc. Based on this knowledge we suggest the model that explains the mechanism behind the lifetime improvement. We argue that the charge accumu

Nowadays, nanoporous films are widely employed in biochemical applications or in opto-photonic devices such as displays, solar cells, or light-guiding systems. In particular, the technological feasibility of nanoporous layers with low refractive indices ha ...

In a molecular semiconductor, a charged molecule experiences a lattice relaxation which reorganizes it into a cation or an anion-radical. This species is not, in general, a polaron. By using calculations of the geometry and the electronic structure both ab initio and at the semi-empirical levels, we have explored the conditions of polaron formation in a molecular model system: oligophenylene-vinylenes, PVs of increasing sizes. The symmetry breaking occurs at sizes larger than five monomers for the anion and

Two novel cyanine-fullerene dyads have been synthesized by means of the Prato reaction from the corresponding cyanine-aldehyde, N-methylglycine and C60. As well as a thorough characterization using MS-TOF, 1H-NMR, 13C-NMR a ...

In a molecular semiconductor, the carrier is dressed with a polarization cloud that we treat as a quantum field of Frenkel excitons coupled to it. The consequences of the existence of this electronic polaron on the dynamics of an extra charge in a material like pentacene can thus be evaluated

The process of hopping transport across organic heterojunctions is critical to the function of organic light-emitting diodes (OLED) and many other currently developed organic electronic devices. We consider the case of a hole-only or homopolar heterojuncti ...

Libero Zuppiroli

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Ultrathin organic transistors on oxide surfaces

Nucleation and growth of ultrathin pentacene films on silicon dioxide: effect of deposition rate and substrate temperature

Comparison between nucleation of pentacene monolayer islands on polymeric and inorganic substrates

Thermopower measurements on pentacene transistors

Quantum Yield Measurement of Fluorescent Zeolite Nanopigments

Doping-induced charge trapping in organic light-emitting devices

On the origin of exciton formation in dye doped Alq(3) OLEDs

Crossover from capacitive to pseudoinductive charge-relaxation in organic/polymeric light-emitting diodes

Fluorescent nanopigments: Quantitative assessment of their quantum yield

Investigation of the charge transport through disordered organic molecular heterojunctions

Efficient blue light-emitting diodes based on a classical "push-pull" architecture molecule 4,4 prime -di-(2-(2,5- dimethoxyphenyl)ethenyl)-2,2 prime -bipyridine

Electrically detected magnetic resonance of organic and polymeric light emitting diodes

Hopping and trapping mechanisms in organic field-effect transistors

Trap-limited transport in rubrene transistors

The mechanism of lifetime extension due to CuPc injection layer in organic light-emitting diodes

Nanoporous films with low refractive index for large-surface broad-band anti-reflection coatings

Polaron formation and symmetry breaking

Synthesis of novel cyanine-fullerene dyads for photovoltaic devices

The impact of molecular polarization on the electronic properties of molecular semiconductors

Charge transport across organic-organic interfaces in organic light-emitting diodes