Search results for "electronics"
showing 10 items of 4340 documents
Phosphomolybdic acid as an efficient hole injection material in perovskite optoelectronic devices.
2018
Efficient perovskite devices consist in a perovskite film sandwiched in between charge selective layers, in order to avoid non-radiative recombination. A common metal oxide used as p-type or hole transport layer is molybdenum oxide. MoO3 is of particular interest for its very large work function, which allows it to be used both as an interfacial charge transfer material as well as a dopant for organic semiconductors. However, high quality and high work function MoO3 is typically thermally evaporated in vacuum. An alternative solution-processable high work function material is phosphomolybdic acid (PMA), which is stable, commercially available and environmentally friendly. In this communicat…
Quantum chemical simulations of doped ZnO nanowires for photocatalytic hydrogen generation
2016
Zinc oxide (ZnO) is considered in general as a promising material for solar water splitting. Its wurtzite-structured bulk samples, however, can be considered as active for photocatalytic applications only under UV irradiation, where they possess ∼1% efficiency of sunlight energy conversion due to their wide band gap (3.4 eV). Although pristine ZnO nanowires (NWs) possess noticeably narrower band gaps than the bulk, the tendency of band gap reduction with increasing NW diameter is insufficient, and further modification is required. We have contributed to filling this gap by performing a series of ab initio calculations on ZnO NWs of different diameters (dNW), which are mono-doped by metal (A…
Boosting inverted perovskite solar cell performance by using 9,9-bis(4-diphenylaminophenyl)fluorene functionalized with triphenylamine as a dopant-fr…
2019
In this study, two newly developed small molecules based on 9,9-bis(4-diphenylaminophenyl)fluorene functionalized with triphenylamine moieties, namely TPA-2,7-FLTPA-TPA and TPA-3,6-FLTPA-TPA, are designed, synthesized and characterized. The electrochemical, optical and thermal properties of both materials are investigated using various techniques. Afterwards, these materials are employed as dopant-free hole transporting materials (HTMs) in planar inverted perovskite solar cell devices with the aim of determining the device performance and studying their stability in comparison with reference N4,N4,N4′′,N4′′-tetra([1,10-biphenyl]-4-yl)-[1,1′:4′,1′′-terphenyl]-4,4′′-diamine (TaTm)-based devic…
Ionic liquid modified zinc oxide injection layer for inverted organic light-emitting diodes
2013
Abstract We have demonstrated a novel approach for fabricating efficient hybrid organic–inorganic light emitting diodes (HyLEDs) by introducing dopants into solutions processable metal oxides as an interfacial layer. The doped ZnO is prepared by adding ionic liquid (IL) to a precursor solution for the ZnO. In this way a heavily doped ZnO:ILs cathode was obtained that enhances the electron injection properties and assures a good wetting of the organic active materials.
First principles modeling of Ag adsorption on the LaMnO3 (001) surfaces
2015
Abstract Doping of oxide surfaces with Ag atoms could improve their catalytic properties, e.g. for solid oxide fuel cell and oxygen permeation membrane applications. We present results of the ab initio calculations of Ag adsorption on the LaMnO 3 (LMO) (001) surfaces. The energetically most favorable adsorption sites for low coverage of Ag atoms and monolayer on both MnO 2 - and LaO-terminations have been determined. The electron charge transfer between Ag and substrate and interatomic distances have been analyzed. The Ag atom migration along the MnO 2 surface is ~ 0.5 eV which could lead to a fast clustering of adsorbates at moderate temperatures whereas the adhesion energy of silver monol…
PbS Nanodots For Ultraviolet Radiation Dosimetry
2011
Lead sulfide (PbS) nanodots in Zirconia (ZrO2) thin film matrix (ZrO2:PbS films) were investigated for UV radiation dosimetry purposes. Samples were fabricated using sol-gel technique. ZrO2:PbS films were irradiated with UV light with wavelengths 250 – 400 nm during 50 minutes. Photoelectron emission spectra of ZrO2:PbS films were recorded and band structure for nonradiated and UV irradiated samples was calculated. It was found that quantity of localized states decreased after UV irradiation while density of localized states was dependent on concentration of PbS nanodots. The observed changes in band structure of ZrO2:PbS films after UV irradiation suggest that the films may be considered a…
Tunable dual-wavelength operation of an all- fiber thulium-doped fiber laser based on tunable fiber Bragg gratings
2018
Tunable dual-wavelength emission of a Tm-doped fiber laser based on two fiber Bragg gratings (FBGs) is experimentally demonstrated. By using two FBGs with central wavelengths at 2069.30 and 2069.44 nm, stable dual-wavelength laser generation in the 2 ?m wavelength region is achieved by adjusting the differential loss of the two wavelengths in the laser cavity. Strain applied on the FBG allows independent tuning of the simultaneously generated wavelengths with separation between the laser lines in a range from 0.54 to 9 nm. The laser has output power fluctuations less than 0.093% for an output power of 77.3 mW.
High-power pulsed dye laser with Fourier-limited bandwidth
1986
A high-peak-power, narrow-linewidth light source with a homogeneous beam profile has been constructed by modifications to a commercially available pulsed-dye-laser system. Output pulses of up to 10 mJ were generated with linewidths of about 50 MHz for 12-nsec pulses. The pulse-to-pulse frequency stability was better than the linewidth, and the center frequency could be scanned over a frequency range of 142.5 GHz at a wavelength of 600 nm. The performance of the system was demonstrated by observing the 6s2 1S0–6s7s1S0 transition in atomic mercury at 2λ = 312.8 nm and the 6s2S1/2–8s2S1/2 transition in atomic gold at 2λ = 308.9 nm using up to 1 mJ of frequency-doubled output for two-photon non…
Nanoscale structural and electrical properties of graphene grown on AlGaN by catalyst-free chemical vapor deposition
2020
The integration of graphene (Gr) with nitride semiconductors is highly interesting for applications in high-power/high-frequency electronics and optoelectronics. In this work, we demonstrated the direct growth of Gr on Al0.5Ga0.5N/sapphire templates by propane (C3H8) chemical vapor deposition (CVD) at temperature of 1350{\deg}C. After optimization of the C3H8 flow rate, a uniform and conformal Gr coverage was achieved, which proved beneficial to prevent degradation of AlGaN morphology. X-ray photoemission spectroscopy (XPS) revealed Ga loss and partial oxidation of Al in the near-surface AlGaN region. Such chemical modification of a 2 nm thick AlGaN surface region was confirmed by cross-sec…
Direct assessment of p–n junctions in single GaN nanowires by Kelvin probe force microscopy
2016
Making use of Kelvin probe force microscopy, in dark and under ultraviolet illumination, we study the characteristics of p-n junctions formed along the axis of self-organized GaN nanowires (NWs). We map the contact potential difference of the single NW p-n junctions to locate the space charge region and directly measure the depletion width and the junction voltage. Simulations indicate a shrinkage of the built-in potential for NWs with small diameter due to surface band bending, in qualitative agreement with the measurements. The photovoltage of the NW/substrate contact is studied by analysing the response of NW segments with p- and n-type doping under illumination. Our results show that th…