E. Petrolati

Series-Connection Designs for Dye Solar Cell Modules

We present a vis-à-vis experimental and PSPICE circuital comparison and optimization of W- and Z-type dye solar cell (DSC) modules. Important design and technological aspects which can, at the same time, promote and hamper each scheme were identified, including differing photocurrents (by a factor 1.6) between front- and back-illuminated cells, sheet-resistance-induced halving of fill factor (FF) when increasing cell width (2-20 mm), and vertical connections with resistances that can affect FF. The modules fabricated showed efficiencies of 4.7% and 4.2% over active area for Z and W modules and 3.4% over total area for both (due to different aperture ratios). Our simulations showed that geometrically optimized front-illuminated DSC Z modules would yield higher efficiencies than W modules built with the same materials if ideal vertical connections can be achieved. Pointers for further differing optimization of each scheme are laid out.

Theory of an electrically injected bulk polariton laser

We present the first simulation of an electrically injected polariton laser device based on Bose–Einstein condensation of exciton polaritons in a bulk GaN microcavity. Our simulator self-consistently describes carrier flow, exciton formation and dissociation, and relaxation of exciton polaritons toward the ground state. We find a density-current threshold of about 50 A/cm2 at room temperature, which could be further improved by using polariton lasers based on quantum wells.

The influence of mobility unbalance on GaN based vertical cavity surface emitting lasers

In this work, we discuss the influence of the large mobility difference between electrons and holes on the electrical injection properties of GaN based vertical cavity surface emitting lasers. This mobility unbalance is mainly responsible for the unfocusing of the electron and hole radiative recombination in the central region of the device where the electromagnetic field is confined.

Multiscale Simulation of Electronic and Optoelectronic Devices with TiberCAD

We present the TiberCAD multiscale device simulation software. The scope of the project is a full description of charge transport and optoelectronic properties of devices with embedded active regions of nanometer-scale. We show simulations of a GaN LED that requires modeling of strain, transport of electrons, holes and excitons and device heating.

Realization of a carbon nanotube-based triode

We report the design and realization of a carbon nanotube-based integrated triode. Patterned Si/SiO2/Nb/Nb2O5multilayer was successfully realized by means of a photolithographic process. Such structure constitutes the patterned substrate of the successive Hot Filament Chemical Vapour Deposition (HFCVD) process. Selective growth of highly oriented SWCNT arrays was obtained in the predefined locations while survival of the entire structure was achieved. Field emission measurements of such materials were carried out both on a diode and in a triode configuration. Good and reproducible field emission behaviour has been observed in several realized structures. In order to validate the experimental data a first simulation of the behaviour of the integrated vacuum triode with a single field emission CNT was also simulated.

Modeling of carbon nanotube-based devices: from nanoFETs to THz emitters

In the first part of the present contribution, we will report on transport calculations of nanoscaled devices based on Carbon Nanotubes obtained via self-consistent density-functional method coupled with non-equilibrium Greens function approaches. In particular, density functional tight-binding techniques are very promising due to their intrinsic efficiency. This scheme allows treatment of systems comprising a large number of atoms and enables the computation of the current flowing between two or more contacts in a fully self-consistent manner with the open boundary conditions that naturally arise in transport problems. We will give a description of this methodology and application to field effect transistor based on Carbon nanotubes. The advances in manufacturing technology are allowing new opportunities even for vacuum electron devices producing radio-frequency radiation. Modern micro and nano-technologies can overcome the typical severe limitations of vacuum tube devices. As an example, Carbon Nanotubes used as cold emitters in micron-scaled triodes allow for frequency generation up to THz region. The purpose of the second part of this contribution will be a description of the modelling of Carbon Nanotube based vacuum devices such as triodes. We will present the calculation of important figures of merit and possible realizations.

PSPICE models for Dye solar cells and modules

A Circuital model for Dye Sensitized Solar Cell is proposed. Experimental comparisons and module design are carried out with the present model.

Simulation of a THz Vacuum Triode Using Carbon-Nanotube Emitter

An analysis and a preliminary evaluation of the performance of an integrated vacuum triode amplifier with a single field emission CNT in the THz frequency range is proposed. The most relevant merit factors, such as leakage current, transparency and cut-off frequency are considered to demonstrate the ability of the device to perform in the THz frequency range

Enhancement of carrier focusing GaN based vertical cavity surface emitting lasers and polariton lasers

We have studied the electron and hole focusing problem observed in gallium nitride (GaN) based microcavity lasers. We outlined the relation between the focusing efficiency and the unbalance between electron and hole mobilities. A new device structure is proposed where the n-layer is on the top of the p-layer, which overcomes the focusing limitation of conventional GaN based vertical cavity surface emitting lasers and polariton lasers.

Innovative design of nano-vacuum triode

An innovative procedure for the realization and the assembly of vacuum triode based on carbon nanotube cold cathode is proposed. The aim of the proposed technique is to avoid the typical problem due to the growth of carbon nanotube in the triode structure. The obtained electrical properties of the realized triode fully confirm the validity of the technique.