Search results for "electronics"

Dynamic doping in bright and stable light emitting electrochemical cells.

2013

By using fast current density and luminance versus voltage (JL-V) analysis the device operation of sandwiched light emitting electrochemical cells (LECs) during their normal voltage driving operation mode is studied. In LECs the application of a voltage results in the movement of ions changing the state of the device, as a result the JL-V scans need to be performed fast and meet certain conditions to be meaningful. Space-charge limited current behavior is observed once the injection barriers are overcome. The increase of the current density after this point imply that the effective thickness of the devices is reduced which indicates the formation of more conductive regions adjacent to the e…

Enhanced Nonlinear Optical Coefficients of MAPbI3 Thin Films by Bismuth Doping

2020

The poor photostability under ambient conditions of hybrid halide perovskites has hindered their recently explored promising nonlinear optical properties. Here, we show how Bi3+ can partially substitute Pb2+ homogeneously in the commonly studied MAPbI3, improving both environmental stability and photostability under high laser irradiation. Bi content around 2 atom % produces thin films where the nonlinear refractive (n2) and absorptive coefficients (β), which modify the refractive index (Δn) of the material with light fluence (I), increase up to factors of 4 and 3.5, respectively, compared to undoped MAPbI3. Higher doping inhibits the nonlinear parameters; however, the samples show higher f…

2021

Gold-assisted mechanical exfoliation currently represents a promising method to separate ultralarge (centimeter scale) transition metal dichalcogenide (TMD) monolayers (1L) with excellent electronic and optical properties from the parent van der Waals (vdW) crystals. The strong interaction between Au and chalcogen atoms is key to achieving this nearly perfect 1L exfoliation yield. On the other hand, it may significantly affect the doping and strain of 1L TMDs in contact with Au. In this paper, we systematically investigated the morphology, strain, doping, and electrical properties of large area 1L MoS2 exfoliated on ultraflat Au films (0.16-0.21 nm roughness) and finally transferred to an i…

Perovskite-Perovskite Homojunctions via Compositional Doping.

2018

One of the most important properties of semiconductors is the possibility of controlling their electronic behavior via intentional doping. Despite the unprecedented progress in the understanding of hybrid metal halide perovskites, extrinsic doping of perovskite remains nearly unexplored and perovskite–perovskite homojunctions have not been reported. Here we present a perovskite–perovskite homojunction obtained by vacuum deposition of stoichiometrically tuned methylammonium lead iodide (MAPI) films. Doping is realized by adjusting the relative deposition rates of MAI and PbI2, obtaining p-type (MAI excess) and n-type (MAI defect) MAPI. The successful stoichiometry change in the thin films is…

Upconversion luminescent nanoparticles in physical sensing and in monitoring physical processes in biological samples.

2015

The most frequently used strategy for sensing is based on the emission variation of a photoactive system and it can be classified as chemical or physical depending on its response to either a chemical or a physical stimulus. There are a large number of luminescent nanomaterials that respond to chemical species, but comparatively, with the exception of temperature sensing, to date there are few examples showing the capacity of photoactive nanosystems responsive to physical stimuli, such as magnetic and electric fields, high radiation energy, tension/pressure, viscosity, etc, and very few of them comprise upconversion nanoparticles (UCNPs). These nanomaterials consist of an inorganic matrix d…

Abrupt-tapered fiber filter arrangement for a switchable multi-wavelength and tunable Tm-doped fiber laser.

2018

A switchable and tunable multi-wavelength Tm-doped fiber laser is successfully demonstrated using a filter constructed with two tapered fiber elements in the cavity. The proposed system design uses a low-cost simple filter that allows stable dual, triple, quadruple, and quintuple-wavelength emission operation in the region around 1.9 μm. In the dual wavelength regime, the laser is capable of independently tuning each wavelength. For switching and tuning, a curvature is applied to the tapered fibers.

Luminescence of ferroelectric crystals: LiNbO3and KNbO3

2000

Abstract The thermostimulated luminescence and time-resolved luminescence of LiNbO3 (congruent, stoichiometric, Eu−, Mn−, or Cr−doped) and KNbO3 crystals (undoped, Fe−, or Mn− doped) excited by X-ray, pulsed nitrogen laser or pulsed electron beam were studied. The luminescence decay times of niobium-oxygen groups (regular or perturbed by defect or impurity) were obtained. It is shown that the energy transfer from bulk to the activator in LiNbO3 is not effective during the electron-hole recombination process.

Signal Amplification in CsPbBr3 Nanoparticle-Doped Photonic Crystal Fibers

2019

Nanoparticles (NPs) have been proved for various photonic and optoelectronic applications with superior performance. Doping holey-fibers with colloidal NPs is an idea with precedents in the optical literature. For example, CdZnS/ZnS core-shell quantum dots (QDs) based lasers at visible wavelengths [1, 2]; and PbS QDs doped fiber amplifiers operating at telecommunication wavelengths [3]. In this paper we harness the potential of photonic crystal fibers (PCFs) doped with chemically synthesized CsPbBr 3 Colloidal-NPs [4] to demonstrate gain functionalities in all-fiber optical microdevices.

Gamma and x-ray irradiation effects on different Ge and Ge/F doped optical fibers

2015

International audience; We performed electron paramagnetic resonance (EPR) measurements on γ and X ray irradiated Ge doped and Ge/F co-doped optical fibers. We considered three different drawing conditions (speed and tension), and for each type of drawing, we studied Ge and Ge/F doped samples having Ge doping level above 4% by weight. The EPR data recorded for the γ ray irradiated fibers confirm that all the samples exhibit a very close radiation response regardless of the drawing conditions corresponding to values used for the production of specialty fibers. Furthermore, as for the X irradiated materials, in the γ ray irradiated F co-doped fibers, we observed that the Ge(1) and the Ge(2) d…

CW and Q-switched diode end-pumped Nd:YAP laser at 1.34 µm. Influence of Nd doping level

2001

A multi watt CW 1.34 µm diode end-pumped Nd:YAP laser is described. Acoustooptic device is tested to obtain Q-switched operation. The influence of the Nd3+ doping level in YAP crystal on the laser efficiency, in CW and in Q-switched mode, is presented.