Framework structure materials in photovoltaics based on perovskites 3D

The inorganic and hybrid organic / inorganic perovskites based on lead halide and derived materials (alloys) having the formula ABX3 are emerging as a new and innovative family of absorber materials for the conversion of solar energy into electricity in photovoltaic systems. Thanks to their composition, perovskites and derivatives have exceptional optical, electrical and structural properties with high absorption of light in the visible solar spectrum and good mobility of charge carriers generated by photons facilitating the extraction of electric current. Due to these important properties, perovskite solar cells combine a high efficiency of conversion of light into electricity with great ease of preparation and synthesis at very low costs via simple deposition techniques. In this article we review the structural and optoelectronic properties of perovskites 3D exhibiting photovoltaic properties, we are also interested in the operating principle of perovskite-based solar cells, charge transport materials and associated architectures. Simple fabrication techniques and issues with stability and hysteresis are also discussed.

Impact of n-Doping Mechanisms on the Molecular Packing and Electron Mobilities of Molecular Semiconductors for Organic Thermoelectrics

Electrical conductivity is one of the key parameters for organic thermoelectrics and depends on both the concentration and mobility of charge carriers. To increase the carrier concentration, molecular dopants have to be added into organic semiconductor materials, whereas the introduction of dopants can influence the molecular packing structures and hence carrier mobility of the organic semiconductors. Herein, we have theoretically investigated the impact of different n-doping mechanisms on molecular packing and electron transport properties by taking N-DMBI-H and Q-DCM-DPPTT respectively as representative n-dopant and molecular semiconductor. The results show that when the doping reactions and charge transfer spontaneously occur in the solution at room temperature, the oppositely charged dopant and semiconductor molecules will be tightly bound to disrupt the semiconductor to form long-range molecular packing, leading to a substantial decrease of electron mobility in the doped film. In contrast, when the doping reactions and charge transfer are activated by heating the doped film, the molecular packing of the semiconductor is slight affected and hence the electron mobility remains quite high. This work indicates that thermally-activated n-doping is an effective way to achieve both high carrier concentration and high electron mobility in n-type organic thermoelectric materials.

Термоэлектрические свойства твердых растворов (CuInSe-=SUB=-2-=/SUB=-)-=SUB=-1-x-=/SUB=-(In-=SUB=-2-=/SUB=-Te-=SUB=-3-=/SUB=-)-=SUB=-x-=/SUB=-

The results of studying the temperature dependences of electrical conductivity, thermoelectric coefficient, Hall mobility of charge carriers, total and electronic thermal conductivity, as well as phonon thermal resistance of alloys of (CuInSe2)1-x(In2Te3)x solid solutions at x=0.005 and 0.0075 are presented. The values ​​of these parameters for certain temperatures were used to calculate the values ​​of the thermoelectric figure of merit of the indicated compositions. It turned out that as the temperature rises, the thermoelectric figure of merit tends to grow strongly, from which it can be concluded that these materials can be used in the manufacture of thermoelements.

Photocatalytic Efficiency of Hybrid Titanium Dioxide Nanowires/Reduced Graphene Oxide (TiO2NWs/RGO) for Degradation of Methyl Orange Dye

The aim of this research is to improve the photocatalytic efficiency by implementation of titanium dioxide nanowires/reduced graphene oxide (TiO2NWs/RGO) hybrid photocatalyst for dye degradation. The hybrid photocatalyst TiO2NWs/RGO was prepared using fabrication method. The physico-chemical properties of the photocatalyst was investigated by FTIR, XRD, SEM TGA, BET and their photocatalytic efficiency was evaluated for methyl orange degradation. Almost 100% of methyl orange was degraded by TiO2NWs/RGO hybrid photocatalyst under UV light within 210 min using 1.0 g at initial concentration of methyl orange were 10 and 20 ppm. This is due to the 1D/2D heterostructures of TiO2NWs/RGO hybrid photocatalyst that leads to the larger surface area, unique morphological and crystallinity properties, as well as excellent mobility of charge carriers and thermally stable structure

Исследование подвижности носителей заряда в слоях нанокристаллов PBS методом полевого транзистора

The field-effect transistor method is used to study the mobility of charge carriers in layers of lead sulfide nanocrystals with ligands of tetrabutylammonium iodide and 1,2-ethanedithiol used to create solar cells. The difference between the operating of a transistor in ambient air and in an inert atmosphere is demonstrated. It is shown that, in the ambient air, the processes of charging nanocrystals are activated when current flows, and the influence of the polarization of the interface of nanocrystals and the insulator on the measurement of the mobility is analyzed. Different reactions of the layers with ligands to light have been demonstrated, showing a significant oxidation of the surface of nanocrystals treated with 1,2-ethanedithiol.

Photoconductivity of Thin Films Obtained from a New Type of Polyindole

The optoelectronic properties of a new poly(2-ethyl-3-methylindole) (MPIn) are discussed in this paper. The absorption and photoluminescence spectra were studied. The electronic spectrum of MPIn showed a single absorption maximum at 269 nm that is characteristic of the entire series of polyindoles. The fluorescence spectra show that the emission peaks of the test sample are centered around 520 nm. The photoconductivity of thin film samples of MPIn polyindole was studied by measuring the current-voltage characteristics under ultraviolet radiation with a wavelength of 350 nm. Samples of phototransistors were obtained, where thin films of MPIn polyindole were used as a transport layer, and their characteristics were measured and analyzed. The value of the quantum efficiency and the values of the mobility of charge carriers in thin polyindole films were estimated.

COMPUTER SIMULATION OF INTERACTIONS OF TETRATHIOPHENE MOLECULES

Надмолекулярная организация сопряженных полимеров сильно влияет на подвижность носителей заряда и, следовательно, на свойства производимых электронных устройств на их основе. Поэтому является важным научится строить вычислительные модели способные воспроизводить структуру таких полимеров с максимально возможной точностью. Одной из главных движущих сил процесса самосборки надмолекулярных структур в сопряженных полимерах является п - п взаимодействие. Его учет является достаточно трудной задачей, особенно при построении мезомасштабных моделей. В данной работе мы используем теорию функционала электронной плотности для отработки методики расчета сопряженных полимеров с учетом п - п взаимодействия. Были изучены геометрические характеристики пачек из четырех молекул тетратиофена. Выполненные расчеты показывают, что использование функционала M06-2X-D3 позволяет корректно моделировать взаимодействия молекул олиготиофенов и структуру образующихся агрегатов, в то время как полуэмпирические расчёты методом PM7 сопряженных полимеров пригодны лишь для быстрой предварительной оптимизации моделей. Разработанная методика расчетов имеет важное значение для параметризации мезомасштабных схем моделирования. The properties of the supramolecular organization of conjugated polymers strongly affect the mobility of charge carriers and, consequently, the properties of produced electronic devices based on them. Therefore, it is important to learn how to build computational models capable of reproducing the structure of such polymers with the highest possible accuracy. One of the main driving forces of the self-assembly of supramolecular structures in conjugated polymers is п-п interaction. Taking it into account is a rather difficult task, especially when constructing mesoscale models. In this work, we use the electron density functional theory to develop a methodology for calculating conjugated polymers taking into account п-п interaction. The geometric characteristics of stacks of four tetra thiophene molecules were studied. The performed calculations show that the use of the M06-2X-D3 functional makes it possible to correctly model the interactions of oligothiophene molecules and the structure of the resulting aggregates, while semiempirical calculations by the PM7 method of conjugated polymers are suitable only for rapid preliminary optimization of models. The tested calculation technique is of great importance for the parametrization of mesoscale modeling schemes. Keywords: organic solar cells, organic polymers, thiophenes, quantum chemical calculations, п-п stacking interaction.

Influence of magnetron sputtering modes on the parameters of ZnO:Ga films

The aim of this work is to study the effect of magnetron sputtering modes - its technological parameters (pressure, substrate temperature and DC power source) on the morphology and electrophysical parameters of nanocrystalline ZnO:Ga films, which can be used as contact layers to nanostructures of photovoltaic converters. It was found that with an increase in the substrate temperature, the grain size decreases from 80 to 30 nm and the film surface roughness, as well as the resistivity from 1.68⋅10−1 to 1.2⋅10−2 Ω⋅cm and the mobility of charge carriers with 18.12 to 5.59 cm2/(V⋅s). In this case, the concentration of charge carriers increases from 5.59⋅1018 to 3.31 ⋅ 1020 cm−3. With an increase in the power of the DC source, the grain size increases from 35 to 90 nm and the surface roughness of the ZnO:Ga films, as well as the concentration of charge carriers from 5.91⋅1018 to 3.35⋅1020 cm−3. In this case, the resistivity decreases from 1.42⋅10−2 to 1.3⋅10−2 Ω⋅cm, and the mobility of charge carriers from 6.74 to 3.22 cm2/(V⋅s). The results obtained can be used in the development of technological processes for the manufacture of highly efficient photoelectric converters.

Kinetic instability of a chitosan – aspartic acid – water system as a method for obtaining nano- and microparticles

The specific electrical conductivity and dielectric constant of aqueous solutions of ionic aminopolysaccharide chitosan in L-aspartic acid were investigated. An increase of the mobility of charge carriers in these solutions was found in comparison with solutions of an individual acid. The evaluation of the kinetic stability revealed that the viscosity, electrical conductivity and dielectric constant of the chitosan – L-aspartic acid – water system decrease, while the pH value increases. It was shown that the time variation of physicochemical and electrochemical parameters is due to the effects of counterionic association with the transition of macromolecules to the ionomeric state and is accompanied by phase segregation of the polymer phase in the form of nano- and microparticles. The conducted studies carried out have shown the fundamental possibility of controlling the metastable state of this system in order to obtain nano- and microparticles.

Investigation of temperature dependences of current-voltage characteristics of hybrid organic materials based on zinc complexes

In this work, we analyzed the current-voltage characteristics in the temperature range of the hybrid organic material C24H24N6O3Zn in order to determine the prospects for using this compound as a semiconductor material. The range of temperature measurements was from 270 to 330 K. An electrochemical analysis of the studied coordination compound was carried out, the energies of the HOMO and LUMO levels were calculated. The method of obtaining, microscopy, and also the method of measuring the temperature dependences of the electrical properties of the obtained thin films of these hybrid materials based on zinc complexes are described. A number of fundamental values of the films of this coordination compound have been calculated: the activation energy is  0.88 eV and the mobility of charge carriers is  1.4710-11 cm V-1 s-1.