96 research outputs found
Study of Lead-Free Perovskite Solar Cells at Elevated Temperatures and UV Irradiatio
In the present work, the change of the electrical performance is
investigated for two lead-free perovskite materials with novel iodide-
based and bromide-based compositions under different exploitation
conditions, such as light-induced stress, elevated temperatures and
ultraviolet light exposure. The charge transport properties are studied in
more detail by spectroscopic methods for the cell with the iodide layer
due to its greater stability, aiming to understand the degradation
mechanism. The results show that this perovskite exhibited excellent
stability at UV exposure and acceptable stability at continuous
illumination at 600 nm. The device is stable up to 55 °C, when the
photovoltage drops. Beyond this threshold temperature, a phase change
transition occurs related to traps formation and charge carriers escaping,
which affects the photovoltage and it slightly increases
Effect of anodizing regimes on the volume expansion factor of the oxide films
The volume expansion factor of porous alumina, formed by through anodizing of an Al foil in ox-
alic and sulphuric acid has been studied. The thickness of obtained porous alumina films was
measured by a mechanical profilometer with a computer signal processing. The volume expansion
factor of porous alumina varied from 1.35 to 1.65. Linear dependences were obtained for the vol-
ume expansion factor of porous alumina versus the anodizing voltage and the ionic current density
logarithm versus the inverse volume expansion factor. Unlike oxide formation in sulphuric acid,
these dependences have two subsequential rectilinear regions in oxalic acid
Applying Aniline for P-doping of PEDOT:PSS Films to Improve Their Conductivity and Efficiency of Perovskite Solar Cells
Poly(3,4- ethylenedioxythiophene):polystyrene sulfonate
(PEDOT: PSS) is responsible for hole extraction efficiency and hole
transport in the perovskite solar cell structure. The inclusion of PSS
reduces the conductivity of the PEDOT films, which inhibits hole
transport and results in a low photo current of the perovskite solar cell.
In this work, an aniline solution was used as an additive in the PEDOT:
PSS thin film to increase electrical conductivity. Two different methods
were used to incorporate the additive: surface and volume treatment.
The results show that the surface treatment with aniline solution can
significantly increase the conductivity of PEDOT: PSS film. Moreover, the photoconversion efficiency of the perovskite solar cell with such a
PEDOT: PSS layer is increased 1.5 times compared to the untreated one
Features of the porous morphology of anodic alumina films at the initial stage of disordered growth
A characteristic feature of disordered porous anodic film growth at the initial stage of aluminum anodizing was revealed by varying the electrolyte type and anodizing voltage. The samples were obtained by the electrochemical oxidation of thin aluminum films (100 nm thick) on SiO2/Si substrates in a 0.3 M oxalic acid at 10–50 V and were studied by SEM. The ImageJ analysis of the images revealed the simultaneous development of two large groups of pores: major pores with a large diameter and minor pores with a smaller diameter. When anodizing in oxalic acid at 10–50 V, it has been shown that the ratio of the diameters of the major and minor pores remains constant and is about 1.17. Using a geometric model, we demonstrated that the centers of the minor pores are located inside the elementary hexagonal cell formed by the centers of the major pores. Moreover, our results are very close to the theoretical value of 2/√3. At the initial stage of disordered pore growth, the development of minor pores rather than major pores is not a random process and is determined by energy-efficient conditions for the development of pores inside the hexagonal cells formed by the major pores. The increase in compressive mechanical stress in the anodic film leads to an interruption in the development of such pores
Recognitionand Analysis of Microstructure Parameters of Porous Anodic Films Using ImageJ
The most important parameters that characterize the microstructure of the films and determine the possibility of their use as porous templates are the pore diameter, porosity, and ordering of the porous structure. Therefore, to increase the efficiency of the use of porous anodic alumina films, it is important to investigate the effect of the formation modes on the microstructure. The aim of this work was to choose and optimize a model for processing experimental data obtained by scanning electron microscopy in the ImageJ to determine the parameters of the microstructure of porous films. The work shows the result of SEMimage analysis and obtains plots of pore diameter distribution by size and determines the diameter of the main pores
Stored charge and its influence on properties of anodic alumina films
In porous and barrier-type anodic alumina films, the stored charge has electronic nature and it plays a significant role in the process of aluminum anodizing. The charge stored can modify the distribution of local field generated by a voltage applied and thus it can affect the oxide growth. The method for the investigation of thermally activated defects in anodic alumina films by reanodizing technique was also described. It was applied for computation of activation energy of electron traps in barrier layer for sulfuric and oxalic acid alumina films and concentration of the traps
Effect of anodic oxygen evolution on cell morphology of sulfuric acid anodic alumina films
The purpose of this work was to study and analyze the effect
of electrolyte temperature and anodization voltage on cell morphology
of thin films of sulfuric acid anodic alumina formed on substrates of
different nature, such as SiO2/Si, glass-ceramic, glass substrates, and
polished aluminum. The data obtained demonstrated that the thermal
conductivity of the substrate in the voltage range from 12 to 14 V
affected a pore diameter (dpore) in anodic films. Depending on the
substrate type, dpore increased in the following order: glass > glass-
ceramic > SiO2/Si > aluminum. It was found that the anodizing voltage
(Ua) of 16 V was a turning point for anodic films obtained in sulfuric
acid after which the slope of the lines for both dpore and Dinter
(interpore distance) vs. Ua changed. This behavior might be explained
by the occurrence of the overpotential enough for the beginning of the
oxygen evolution reaction. We assumed that the oxygen evolution on
aluminum oxide surface at the pore bottom at Ua> 16 V results in an
increase in acid concentration in the solution and, consequently, in rise
in acidic nature of the electrolyte and increase in the dissolution rate of
the oxide layer of pore walls
Novel Electrochemical Aptasensor Based on Ordered Mesoporous Carbon/2D Ti3C2 MXene as Nanocarrier for Simultaneous Detection of Aminoglycoside Antibiotics in Milk
Herein, a novel electrochemical aptasensor using a broad-spectrum aptamer as a biorecognition element was constructed based on a screen-printed carbon electrode (SPCE) for simultaneous detection of aminoglycoside antibiotics (AAs). The ordered mesoporous carbon (OMC) was firstly modified on 2D Ti3C2 MXene. The addition of OMC not only effectively improved the stability of the aptasensor, but also prevented the stacking of Ti3C2 sheets, which formed a good current passage for signal amplification. The prepared OMC@Ti3C2 MXene functioned as a nanocarrier to accommodate considerable aptamers. In the presence of AAs, the transport of electron charge on SPCE surface was influenced by the bio-chemical reactions of the aptamer and AAs, generating a significant decline in the differential pulse voltammetry (DPV) signals. The proposed aptasensor presented a wide linear range and the detection limit was 3.51 nM. Moreover, the aptasensor, with satisfactory stability, reproducibility and specificity, was successfully employed to detect the multi-residuals of AAs in milk. This work provided a novel strategy for monitoring AAs in milk
The sorption of water molecules in the pores of anodic alumina films during aluminum anodizing in oxalic acid
The thermogravimetric analysis of membranes of anodic aluminum oxide (AAO) was carried out. The results showed that in the process of anodic growth, water molecules are adsorbed in the pores of Al2O3, the amount of which is determined by the anodizing voltage of aluminum. The relationship is revealed and the graphs of the relationship between anodizing voltage, annealing temperature, and weight loss of nanostructured membranes of AAO are presented. It has been established that the adsorption of water molecules on the surface of AAO is explained by the presence of a surface charge, which disappears after annealing at 200–300 °C. An increase in the amount of adsorbed water with an increase in the anodizing voltage from 20 to 40 V indicates a decrease in the surface charge density
Electrical behaviour, characteristics and properties of anodic aluminium oxide films coloured by nickel electrodeposition
Porous anodic films on 1050 aluminium substrate were coloured by AC electrodeposition of nickel. Several experiments were performed at different deposition voltages and nickel concentrations in the electrolyte in order to correlate the applied electrical power to the electrical behaviour, as well as the characteristics and properties of the coatings. The content of nickel inside the coatings reached 1.67 g/m2, depending on the experimental conditions. According to the applied AC voltage in comparison with the threshold voltage Ut, the coating either acted only as a capacitor when U\Ut and, when U[Ut, the behaviour during the anodic and cathodic parts of the power sine wave was different. In particular, due to the semi-conducting characteristics of the barrier layer, additional oxidation of the aluminium substrate occurred during the anodic part of the electrical signal, whilst metal deposition (and solvent reduction) occurred during the cathodic part; these mechanisms correspond to the blocked and pass directions of the barrier layer/electrolyte junction, respectively
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