Search results for "optoelectronic"
showing 10 items of 2328 documents
How does graphene enhance the photoelectric conversion efficiency of dye sensitized solar cells? An insight from a theoretical perspective
2019
The main goal of this work is to clearly answer the question from a theoretical perspective: how does graphene enhance the photoelectric conversion efficiency in the semiconducting layer of a dye sensitized solar cell? Several arrangements of the graphene layer between the dye molecule and the TiO2 (101) surface are carefully studied and discussed. The dynamic interfacial electron propagations are simulated with consideration of the underlying nuclear motion effect. Theoretical investigation shows that graphene can speed up the electron injection from the dye molecules to the semiconductor layer, only when the graphene sheet is bonded to the TiO2 surface via C–Ti bonds. The excited electron…
Miniature magnetic devices for laser-based, table-top free-electron lasers
2007
Truly table-top sized radiation sources based on compact laser-plasma accelerators require compact and strong focusing devices and efficient short-period undulators. Complementing our recent theoretical work on the feasibility of a table-top FEL, we here present the design and successful experimental characterizations of a 5 mm period length undulator and miniature quadrupole magnets with field gradients of the order of $500\text{ }\text{ }\mathrm{T}/\mathrm{m}$.
Frequency comb generation in whispering gallery mode silica microsphere resonators
2021
Optical frequency combs (OFC) using different kinds of whispering-gallery-mode (WGM) microresonators have already shown different applications and especially their applications in fiber optical communication systems as replacements of laser-arrays. For this application the free spectral range (FSR) of 200 GHz or less is desirable. Besides the fabrication material for microspheres, the resonator radius can be modified to change the FSR. In this paper use of silica microspheres for OFC represents an inexpensive alternative over the other microcombs: microring, microdisk, and microtoroid. We experimentally present a microsphere fabrication process from a different kind of silica (SiO2) fibers …
Thermally Tunable Surface Acoustic Wave Cavities
2020
We experimentally demonstrate the dynamical tuning of the acoustic field in a surface acoustic wave (SAW) cavity defined by a periodic arrangement of metal stripes on LiNbO3 substrate. Applying a dc voltage to the ends of the metal grid results in a temperature rise due to resistive heating that changes the frequency response of the device up to 0.3%, which can be used to control the acoustic transmission through the structure. The timescale of the switching is demonstrated to be of about 200 ms. In addition, we have also performed finite-element simulations of the transmission spectrum of a model system, which exhibits a temperature dependence consistent with the experimental data. The adv…
Interface engineering in efficient vacuum deposited perovskite solar cells
2016
Abstract We studied the effect of the charge transport layers in p-i-n perovskite solar cells using vacuum deposited methylammonium lead iodide thin-film absorbers. While solution-processed perovskite films are frequently deposited directly on PEDOT:PSS leading to good solar cell performances, in some cases even to very good Voc values, we show that in devices employing vacuum deposited MAPbI3 perovskites, the removal of the polyTPD electron blocker substantially reduces the photovoltaic behavior. This is indicative of rather different charge transport properties in the vacuum deposited MAPbI3 perovskites compared to those prepared from solution. On the other hand, we investigated the use o…
Structure-determined thermoelectric properties of Bi2Se3 thin films deposited by vapour-solid technique
2018
International audience; In this work, a simple catalyst-free vapour-solid deposition method is applied for controlled obtaining of two types (planar and disordered) continuous Bi2Se3 nanostructured thin films on different (fused quartz/glass, mica, graphene) substrates. Performed for the deposited thin films transport and thermoelectric characterization (type, concentration and mobility of the main charge carriers, Seebeck coefficient and power factor) showed that proposed deposition method allows to fabricate “low-doped” Bi2Se3 thin films with power factor comparable and even higher than reported for the Bi2Se3 thin films fabricated by molecular beam epitaxy technique.
Multiexciton complex from extrinsic centers in AlGaAs epilayers on Ge and Si substrates
2013
The multiexciton properties of extrinsic centers from AlGaAs layers on Ge and Si substrates are addressed. The two photon cascade is found both in steady state and in time resolved experiments. Polarization analysis of the photoluminescence provides clearcut attribution to neutral biexciton complexes. Our findings demonstrate the prospect of exploiting extrinsic centers for generating entangled photon pairs on a Si based device. © 2013 AIP Publishing LLC.
Indium surfactant effect on AlN/GaN heterostructures grown by metal-organic vapor-phase epitaxy: Applications to intersubband transitions
2006
We report on a dramatic improvement of the optical and structural properties of AlN/GaN multiple quantum wells (MQWs) grown by metal-organic vapor-phase epitaxy using indium as a surfactant. This improvement is observed using photoluminescence as well as x-ray diffraction. Atomic force microscopy shows different surface morphologies between samples grown with and without In. This is ascribed to a modified relaxation mechanism induced by different surface kinetics. These improved MQWs exhibit intersubband absorption at short wavelength (2 mu m). The absorption linewidth is as low as 65 meV and the absorption coefficient is increased by 85%.
Design of dispersion-managed fiber systems for transmitting chirp-free Gaussian pulses
2008
International audience; We present a general method to analytically design a dispersion-managed (DM) fiber system for any desired fiber (dispersion, nonlinearity and losses) and pulse (width and energy) parameters. This analytical design allows one to transmit chirp-free Gaussian pulses (for very long distances) in almost all kinds of DM fiber systems that have appeared so far in the literature, including systems with dispersion map length greater, equal or shorter with respect to the amplification period.
Preface to Special Issue of Energy Technology on Perovskite Optoelectronics
2017
This Editorial introduces one of two companion Special Issues on “Halide Perovskites for Optoelectronics Applications” in Energy Technology and ChemSusChem following the ICMAT 2017 Conference in Singapore. More information on the other Special Issue can be found in the Editorial published in ChemSusChem.