Search results for "Heterojunction"

Plasmonic stratified devices for superlensing in the self-focusing regime

2012

We show that diffraction-management of subwavelength scattered fields assisted by metallodielectric heterostructures leads to superresolving imaging. An accurate design of a passive multilayered compound provides nearly aberration-free images with subwavelength resolution out of the canalization regime even using optical paths longer than a wavelength.

Molecular Engineering of Porphyrin‐Tapes/Phthalocyanine Heterojunctions for a Highly Sensitive Ammonia Sensor

2020

International audience; Modulating the interfacial charge alignments by molecular engineering in an organic heterojunction device is a smart strategy to improve its conductivity, which can be exploited in high performance gas sensors development. Herein, the fabrication of new organic heterojunction devices based on porphyrin tapes and phthalocyanines and their potentiality in ammonia sensing at different relative humidity (rh) are investigated. The devices are built using dry approach relying on oxidative chemical vapor deposition for simultaneous synthesis, doping and deposition of the porphyrin tape layer and physical vapor deposition of phthalocyanine layer. The association of the porph…

Spontaneous core–shell elemental distribution in In-rich In(x)Ga1-xN nanowires grown by molecular beam epitaxy.

2014

International audience; The elemental distribution of self-organized In-rich InxGa1-xN nanowires grown by plasma-assisted molecular beam epitaxy has been investigated using three different techniques with spatial resolution on the nanoscale. Two-dimensional images and elemental profiles of single nanowires obtained by x-ray fluorescence and energy-dispersive x-ray spectroscopy, respectively, have revealed a radial gradient in the alloy composition of each individual nanowire. The spectral selectivity of resonant Raman scattering has been used to enhance the signal from very small volumes with different elemental composition within single nanowires. The combination of the three techniques ha…

Organoboron Polymers for Photovoltaic Bulk Heterojunctions

2010

Modifications électrochimiques de surfaces et dispositifs électroniques organiques

2018

Organic electronics remains a fruitful research field thanks to the diversity of molecular structures reachable by organic synthesis. Molecular materials offer convenient shaping processes, such as solution processing techniques, which can be used for the fabrication of organic devices on plastic substrates.Our works can be summarized as the elaboration of conductometric devices thanks to electrochemistry and the study of their electrical and sensing properties. They deal with two topics: the development of new transducers based on substituted polyanilines and phthalocyanines and the study of the influence of electrochemical modifications on the behavior of known devices.We first developped…

LIQUIDI IONICI E FULLERENI: PIATTAFORME PER NUOVI MATERIALI

The synthesis of innovative catalysts based on different carbon nanoforms (CNFs), namely fullerene C60 and carbon nanotubes (CNTs), and their application in Suzuki and Heck C-C coupling reactions, constitutes the common thread of the first part (Chapter 1 and 2) of this thesis. C60 and CNTs were functionalized with ionic liquids (ILs) and poly-amidoamine (PAMAM) dendrimers, respectively, and used as supports for palladium nanoparticles (PdNPs). Moreover, additional supported catalytic systems based on one of the synthesized C60-IL hybrids were prepared and successfully employed in the title coupling reactions. The final part (Chapter 3) of the thesis deals on the microwave-mediated synthesi…

Preparation and photocatalytic activity of ZnO-SnO2, ZnO-ZnWO4 and SnO2-ZnO-ZnWO4 nanocomposites

2014

Electrical characterization of high-efficiency bifacial silicon solar cells

2018

This work presents a preliminary study on the electrical characterization of high efficiency bifacial solar cells. An opening discussion on the state-of-the-art of such advanced technology is initially proposed and the experimental characterization of some prototypes is described. From this analysis, it can be stated that the bifacial silicon solar cells can be a very promising technology with high electrical performances and efficiency.

Solar blind detectors based on AlGaN grown on sapphire

2005

Solar blind detectors have been fabricated based on AlGaN heterostructures grown on sapphire by molecular beam epitaxy or chemical vapour deposition. MSM and Schottky detectors were investigated. High performance devices have been obtained thanks to an optimization of the material crystalline quality (including the suppression of cracks) and of the process. We show that the spectral limitations of MSM detectors are dictated by intrinsic phenomena that are analysed in details while the responsivity and detectivity also depends on the technological process with a special emphasis on the geometry of finger and contact pads. One and two dimensional arrays have been fabricated and preliminary re…

Density of States characterization of TiO2 films deposited by Pulsed Laser Deposition for Heterojunction solar cells

2021

The application of titanium dioxide (TiO2) in the photovoltaic field is gaining traction as this material can be deployed in doping-free heterojunction solar cells with the role of electron selective contact. For modeling-based optimization of such contact, knowledge of the titanium oxide defect density of states is crucial. In this paper, we report a method to extract the defect density through nondestructive optical measures, including the contribution given by small polaron optical transitions. The presence of both related to oxygen-vacancy defects and polarons is supported by the results of optical characterizations and the evaluation of previous observations resulting in a defect band …