Search results for "Photocurrent"

Dielectric properties of potassium–sodium niobate ceramics at low frequencies

2016

ABSTRACTA study of the effects of ageing history on the electrical properties of lead-free ferroelectric ceramics of (K0.5Na0.5)(Nb1−xSbx)O3 + 0.5 mol% MnO2 and (K0.5Na0.5)(Nb1−xTax)O3 + 0.5 mol%MnO2 for x = 0.05 is reported. The samples after storage at a constant temperature have been subject to infra-low-frequency electric field and radiation. Differences of the photoelectric response between the two examined compounds were found and the restoration of polarisation in the aged ceramic materials by cycles of applied field is discussed.

Luminescence dynamics of hybrid ZnO nanowire/CdSe quantum dot structures

2016

Colloidal CdSe quantum dots (QDs) functionalized with different organic linker molecules are attached to ZnO nanowires (NWs) to investigate the electron transfer dynamics between dots and wires. After linking the quantum dots to the nanowires, the photo-induced electron transfer (PET) from the QDs into the NWs becomes visible in the PL transients by a decrease of dot luminescence decay time. The different recombination paths inside the QDs and the PET process are discussed in the framework of a rate equation model. Photoconductivity studies confirm the electron transfer by demonstrating a strong enhancement of the wire photocurrent under light irradiation into the dot transition. (© 2016 WI…

A procedure to evaluate the seven parameters of the two-diode model for photovoltaic modules

2019

Abstract The paper presents an analytical procedure to calculate the seven parameters of the two-diode model of photovoltaic (PV) panels for any value of the solar irradiance and cell temperature. Six parameters (the photocurrent, the diode reverse saturation currents, the quality factor of the first diode and the series and shunt resistances), are evaluated by solving the equations related to the properties of the main points of the current-voltage (I-V) characteristics. The further information, necessary to calculate the entire set of seven truly independent parameters, is based on two conditions that have to be simultaneously satisfied: 1) the exclusion of negative values of the model pa…

High-efficiency silicon-compatible photodetectors based on Ge quantum dots

2011

We report on high responsivity, broadband metal/insulator/semiconductor photodetectors with amorphous Ge quantum dots (a-Ge QDs) as the active absorbers embedded in a silicon dioxide matrix. Spectral responsivities between 1-4 A/W are achieved in the 500-900 nm wavelength range with internal quantum efficiencies (IQEs) as high as ∼700%. We investigate the role of a-Ge QDs in the photocurrent generation and explain the high IQE as a result of transport mechanisms via photoexcited QDs. These results suggest that a-Ge QDs are promising for high-performance integrated optoelectronic devices that are fully compatible with silicon technology in terms of fabrication and thermal budget. © 2011 Amer…

Effect of Reynolds number and lithium cation insertion on titanium anodization

2016

This work studies the influence of using hydrodynamic conditions (Reynolds number, Re = 0 to Re = 600) during Ti anodization and Li+ intercalation on anatase TiO2 nanotubes. The synthesized photocatalysts were characterized by using Field Emission Scanning Electron Microscope (FE-SEM), Raman Confocal Laser Microscopy, Electrochemical Impedance Spectroscopy (EIS), Mott-Schottky analysis (M-S), photoelectrochemical hydrogen production and resistance to photocorrosion tests. The obtained results showed that the conductivity of the NTs increases with Li+ intercalation and Re. The latter is due to the fact that the hydrodynamic conditions eliminate part of the initiation layer formed over the tu…

Should TiO2 nanostructures doped with Li+ be used as photoanodes for photoelectrochemical water splitting applications?

2017

[EN] Different TiO2 nanostructures, nanotubes and nanosponges, were obtained by anodization of Ti under stagnant and hydrodynamic conditions. Samples were doped with Li+ before and after annealing at 450 degrees C during 1 h. The nanostructures were characterized by different microscopy techniques: Field Emission Scanning Electron Microscopy (FE-SEM) and Raman Confocal Laser Microscopy. Additionally, Incident Photon-to-electron Conversion Efficiency (IPCE), photoelectrochemical water splitting and stability measurements were also performed. According to the results, TiO2 nanostructures doped before annealing present the worst photocurrent response, even if compared with undoped samples. On …

Characterization of Anodic Oxides on Titanium by Photocurrent and Differential Admittance Techniques

2010

Characterization of Anodic Oxides on Magnetron Sputtered Ta-Nb Alloys by Photocurrent Spectroscopy and Differential Admittance Measurements

2010

Identification of passive layers on Co in Alkaline solutions by photocurrent spectroscopy

2005

The photoelectrochemical behavior of passive films on Co has been studied as a function of the polarizing voltage and electrolyte composition. Passive layers formed at 0 V (standard hydrogen electrode, SHE) in 0.1 M NaOH consisted of Co(OH) 2 , whose bandgap value has been found to be 1.85 eV. Higher bandgap values (2.75 eV) have been measured for passive films formed in borate buffer at 0 V (SHE), which are mainly consist of CoO. The Eg values have been related to the film composition on the basis of a correlation between the bandgap of passive films and the electronegativity of their constituents.

A simple method to fabricate high-performance nanostructured WO3 photocatalysts with adjusted morphology in the presence of complexing agents

2017

[EN] The rich and complex chemistry of tungsten was employed to synthesize innovative WO3 nanoplatelets/nanosheets by simple anodization in acidic electrolytes containing different concentrations of complexing agents or ligands, namely F- and H2O2. The morphological and photoelectrochemical properties of these nanostructures were characterized. The best of these nanostructures generated stable photocurrent densities of ca. 1.8 mA cm(-2) at relatively low bias potentials (for WO3) of 0.7 V-Ag/AgCl under simulated solar irradiation, which can be attributed to a very high active surface area. This work demonstrates that the morphology and dimensions of these nanostructures, as well as their ph…