Search results for "Solid-State"

Photoluminescence Imaging and LBIC Characterization of Defects in mc-Si Solar Cells

2018

Today’s photovoltaic market is dominated by multicrystalline silicon (mc-Si) based solar cells with around 70% of worldwide production. In order to improve the quality of the Si material, a proper characterization of the electrical activity in mc-Si solar cells is essential. A full-wafer characterization technique such as photoluminescence imaging (PLi) provides a fast inspection of the wafer defects, though at the expense of the spatial resolution. On the other hand, a study of the defects at a microscopic scale can be achieved through the light-beam induced current technique. The combination of these macroscopic and microscopic resolution techniques allows a detailed study of the electric…

Tunable Eu2+ emission in KxNa1 − xLuS2 phosphors for white LED application

2016

Set of Eu2+-doped KxNa1 − xLuS2 phosphors (x = 0–1) in the form of transparent crystalline hexagonal platelets was successfully synthesized by chemical reaction under the flow of hydrogen sulfide. Their physical properties were investigated by means of X-ray diffraction, X-ray fluorescence, time-resolved luminescence spectroscopy and electron paramagnetic resonance. Special attention was given to photoluminescence emission spectra under the 395 nm and 455 nm excitation aiming to obtain white emission with tunable color temperature. EPR method was employed to understand the Eu2+ incorporation and distribution in the KxNa1 − xLuS2 hosts. CIE xy-coordinates were calculated to compare effects o…

Synthesis, characterization and solid-state photoluminescence studies of six alkoxy phenylene ethynylene dinuclear palladium(II) rods

2015

A rare family of six discrete binuclear [PdCl(PEt3)2] phenylene ethynylene rods with alkoxy side chains (methoxy, ethoxy and heptoxy) have been developed, and their solid-state photoluminescence results have been presented and discussed. The shorter bridging ligands are of the general formula H–CuC– C6H2(R)2–CuC–H, where R = H, OCH3, OC 2H5, and OC7H15, whereas the longer ones are based on H– CuC–C6H4–CuC–C6H2(R)2–CuC–C6H4–CuC–H, where R = OCH3, OC 2H5. These ligands display increasing length in both the main dimension (backbone length) as well as the number of carbons in the side chains (R, alkoxide side chain) that stem from the central phenylene moiety. The X-ray crystal structures of tw…

SiPMs coated with TPB: coating protocol and characterization for NEXT

2012

[EN] Silicon photomultipliers (SiPM) are the photon detectors chosen for the tracking readout in NEXT, a neutrinoless \bb decay experiment which uses a high pressure gaseous xenon time projection chamber (TPC). The reconstruction of event track and topology in this gaseous detector is a key handle for background rejection. Among the commercially available sensors that can be used for tracking, SiPMs offer important advantages, mainly high gain, ruggedness, cost-effectiveness and radio-purity. Their main drawback, however, is their non sensitivity in the emission spectrum of the xenon scintillation (peak at 175 nm). This is overcome by coating these sensors with the organic wavelength shifte…

Impact of nitrogen doping on the band structure and the charge carrier scattering in monolayer graphene

2021

The addition of nitrogen as a dopant in monolayer graphene is a flexible approach to tune the electronic properties of graphene as required for applications. Here, we investigate the impact of the doping process that adds N dopants and defects on the key electronic properties, such as the mobility, the effective mass, the Berry phase, and the scattering times of the charge carriers. Measurements at low temperatures and magnetic fields up to 9 T show a decrease of the mobility with increasing defect density due to elastic, short-range scattering. At low magnetic fields weak localization indicates an inelastic contribution depending on both defects and dopants. Analysis of the effective mass …

Flashlamp-pumped Ti:Sapphire laser with different rods grown by Czochralski and Verneuil methods

1992

The design and the development of a flashlamp-pumped Ti:Sapphire laser is described. Design criteria are discussed and performance improvements using different types of fluorescent UV converters or filters, such as organic dyes or doped glass are presented. We have tested different laser rods at various Ti-concentrations obtained by Verneuil or Czochralski growth techniques. The maximum laser output energy of 540 mJ with a differential efficiency up to 1% was achieved by using only a pyrex filter surrounding the laser rod.

1971

Characteristics of laser operation at 1064 nm in Nd:YVO_4 under diode pumping at 808 and 914 nm

2011

International audience; A comparative study between 808 and 914nm pumping of Nd:YVO4 crystals for laser operation at 1064nm has been carried out. Using similar setups, performances of both configurations were first studied in the continuous wave, small-signal gain, and Q-switched regimes. Thanks to a numerical model, it is shown that fluorescence quenching and upconversion processes limit the possible uses for the 914nm pumping scheme to regimes with low population inversions

Preparation of Catalysts and Photocatalysts Used for Similar Processes

2019

Abstract This chapter reports the main techniques used to synthesize powders and films of heterogeneous catalysts and photocatalysts, often used for similar processes. Traditional preparation processes of bulky (photo)catalysts including precipitation, sol–gel technique, hydrothermal or solvothermal method, solid-state reactions, and flame syntheses were briefly described. The sonochemical method and microwave irradiation technique were also considered. The syntheses of supported catalysts by different techniques, including deposition–precipitation, impregnation, and wet coating technologies were also described. Moreover, a survey is reported of methods to deposit thin films of catalysts on…

Characterization of the Solid State Properties of Anodic Oxides on Ta-Nb Alloys as a Function of the Anodizing Conditions

2011

Tantalum oxide, niobium oxide and Ta-Nb containing mixed oxides were grown by anodizing sputter-deposited TaxNb(1-x) alloys with 0 ≤ x ≤ 1. A photoelectrochemical investigation was performed in order to estimate the band gap values of the oxides as a function of their composition as well as to estimate their flat band potential. Differential capacitance curves were recorded for all the investigated oxides in a wide range of electrode potential and for several frequencies of the alternative signal. The dependence of C on the applied potential and a.c. frequency was interpreted on the basis of amorphous semiconductor Schottky barrier, and allowed to estimate the dielectric constant of the inv…