Photoelectric Structures Research Articles

Spectral Singularities of the Photoelectric Effect in a Zinc Phthalocyanine–Fullerene (ZnPc:C70) Donor–Acceptor Blend

Spectral singularities of the ampere–watt sensitivity of photoelectric structures consisting of a transparent indium–tin oxide electrode, a photosensitive organic layer, and an aluminum electrode have been studied. The structures have been formed on a quartz glass substrate. The photosensitive layer has been vacuum-evaporated either from zinc phthalocyanine ZnPc (exhibiting donor properties) and C70 fullerene (acceptor) organic precursors or from a ZnPc:Cr70 donor–acceptor blend. Using computer simulation, the structure of absorption bands has been determined in a wide spectral range for all three above systems. This has made it possible to calculate the absorbed and reflected fractions of radiation incident on the sample and explain the singular spectral behavior of the ampere–watt sensitivity of the ZnPc:C70 blend. It has been shown that the photosensitivity of the blend reaches a maximum near the overlap of the absorption bands of donor and acceptor molecules

Electrical and Optical Characteristics of CsPbI-=SUB=-3-=/SUB=- and CsPbBr-=SUB=-3-=/SUB=- Lead Halide Perovskite Nanocrystal Films Deposited on c-Si Solar Cells for Photovoltaic Applications

The deposition of an additional layer of nanoparticles is a widely used method for improving the optical and electrical characteristics of semiconductor solar cells (SCs). In this work, films of nanocrystals (NC) of inorganic perovskites of lead halides CsPbI3 and CsPbBr3 are deposited on the surface of a solar cell based on crystalline silicon (c-Si). It is shown that the optical properties of such NC films are in good agreement with the optical properties of c-Si. It has been found that the absorption coefficient of solar cells with NC layers of inorganic perovskites is much higher in the visible region of the spectrum, which increases the photocurrent generation in the SC in the range of 370-900 nm. A significant effect of surface roughness on the photoelectric properties of solar cells has been found. CsPbI3 NC films have a textured surface and higher photocurrent than CsPbBr3 NC films, which are rougher. Enhanced photovoltaic properties of photoelectric structures with a CsPbI3 NC layer compared to CsPbBr3 NC films due to their lower degree of roughness were observed. Keywords: perovskite nanocrystals, silicon solar cells, reflection spectra, photoluminescence, electrical conductivity.

Femtosecond Laser Precision Engineering: From Micron, Submicron, to Nanoscale

As a noncontact strategy with flexible tools and high efficiency, laser precision engineering is a significant advanced processing way for high-quality micro-/nanostructure fabrication, especially to achieve novel functional photoelectric structures and devices. For the microscale creation, several femtosecond laser fabrication methods, including multiphoton absorption, laser-induced plasma-assisted ablation, and incubation effect have been developed. Meanwhile, the femtosecond laser can be combined with microlens arrays and interference lithography techniques to achieve the structures in submicron scales. Down to nanoscale feature sizes, advanced processing strategies, such as near-field scanning optical microscope, atomic force microscope, and microsphere, are applied in femtosecond laser processing and the minimum nanostructure creation has been pushed down to ~25 nm due to near-field effect. The most fascinating femtosecond laser precision engineering is the possibility of large-area, high-throughput, and far-field nanofabrication. In combination with special strategies, including dual femtosecond laser beam irradiation, ~15 nm nanostructuring can be achieved directly on silicon surfaces in far field and in ambient air. The challenges and perspectives in the femtosecond laser precision engineering are also discussed.

Influence of Radiation Defects Induced by Low-Energy Protons at a Temperature of 83 K on the Characteristics of Silicon Photoelectric Structures

Irradiation by low-energy products leads to a variation in the electrical, optical, and other properties of the surface layer of semiconductor structures, which gives additional possibilities to modify semiconductor devices. This work is devoted to investigating the influence of radiation defects induced by low-energy protons at a sample temperature of 83 K on the properties of double-sided silicon photoelectric structures with a diffusion n+–p junction. Samples of the n+–p–p+ type are irradiated by a proton flux with a dose of 1015 cm–2 and energy of 40 or 180 keV. To explain the observed regularities of varying the parameters of the current–voltage characteristics and transmission coefficients, the distribution of the average number of interstitial silicon, vacancies, divacancies, and disordered regions formed under these conditions per length unit of the projected path by one proton in the diffusion layer in the space-charge region of the n+–p junction is calculated. It is shown that protons with an initial energy of 40 keV preferentially vary the physical properties of the layer with a high concentration of donors, while protons with an initial energy of 180 keV vary the properties of the space-charge region in the layer containing acceptors. The number of radiation-induced defects at the maximum of the spatial distribution in the n-type region is much smaller than in the p-type region.

Study of the effect of local photon annealing on stress in silicon wafers

The effect of photon annealing on deformation in the crystal structure of boron doped Cz-Si wafers has been studied using triple crystal X-ray diffraction. Conventional annealing of the entire surface of double-side polished silicon wafers with halogen lamps (photon annealing mode) and rapid thermal annealing produce compression deformation. Annealing with special phototemplate providing for local annealing of multiple separated wafer areas (local photon annealing mode) at relatively low wafer temperatures (less than 55 °C) produces tensile deformation. This effect however is not observed if the reverse side of the annealed wafer contains a mechanical gettering layer. A mechanism explaining the experimental results has been suggested and can be used for the synthesis of charge pumps in photoelectric converter structures.

Modern problems and working out of the new method of measurement of characteristics of laser radiation

In this work the new way of measurement of capacity of IR–radiation by means of silicon photo–electric structures is offered and developed. Results of test are resulted and the new way is scientifically proved.

Photoelectric detecting properties of perovskite manganite and their application in the petroleum fields

The traditional optical sensors cannot meet the demand in the harsh environment as the scope of oil exploration become deeper and deeper. New types of photoelectric detectors which can work in the high temperature and pressure environment and also have high performances in photoelectric sensitivity and responsivity are of great significance. This paper summarize our recent advances of photoelectric detectors based on perovskite manganite oxides working in at high temperature. We fabricated photoelectric detector structures by deposited manganite films on different substrates. We systemically study the properties of the detector and enhance the photovoltaic sensitivity by various ways. We also focus on the photoelectric properties with the temperature increasing to 500 degree centigrade and find that the tilted manganite film shows stability of photovoltaic response at the high temperature. These results not only help to reveal the physical mechanism of the electron strong correlation system, but also show an attractive potential application in petroleum exploration and oil wells security fields.

Influences of lattice mismatches on equilibrium morphologies and strain distributions of quantum dots

The morphologies of quantum dots and distributions of stresses in and around quantum dots structures have a significant effect on photoelectric properties and electronic structures. Optical and electronic devices of different efficiencies based on quantum dots can be manufactured by choosing self-assembly of different materials to control epitaxial growth. In this article we investigate the equilibrium morphologies and the strain distributions of self-assembled pyramidal semiconductor quantum dots in Stranski-Krastanov growth mode based on the finite element method of the anisotropic theory of elasticity. We also give the equilibrium morphologies and the distribution of the stress and the strain, the hydrostatic strain and the biaxial strain for different lattice mismatched quantum dots. The results can serve as a basis for interpretation of experiments.

Growth of the (In2S3) x (FeIn2S4)1 − x single crystals and properties of photoelectric structures on their basis

Complete mutual solubility in the (In2S3) x (FeIn2S4)1 − x system is established. The technology is developed, and single crystals of the continuous series of the (In2S3) x (FeIn2S4)1 − x solid solutions are grown for the first time. The linear dependence of the unit cell parameter of single crystals with a cubic spinel lattice on the solid solution composition is found. First, photosensitive Schottky barriers are fabricated, and then, based on studies of their photosensitivity, the character of band-to-band transition is discussed and the values of the band gap depending on the atomic composition are estimated. The possibility of using the obtained solid solutions as broadband photoconverters of optical radiation is revealed.

Photoelectric structures based on nanoporous p-InP

The possibility of nanostructuring of surfaces of indium phosphide with hole conduction is confirmed. The technique of manufacturing and research of SnO2/InP heterostructures with a nanoporous surface at the interface is developed. It is shown that the investigated structure can form a basis for working out photovoltaic devices with an enlarged active surface.

Discrete space charge aberrations in spherical photoelectric emission structures

Concentric spherical photoelectron diode structures can be used to generate high current densities when illuminated with intense laser beams. For applications in electron microscopy and for beam source applications, trajectory aberrations of the emitted particles are important. This paper describes Monte Carlo estimations of trajectory fluctuations produced by discrete-charge interactions in a laser-driven spherical photoemission structure. The trajectory of one photoelectron traveling in the presence of 125 randomly positioned neighbors is computed, and its apparent source position is determined as it arrives at the anode. Hundreds of such passes are averaged to estimate the aberration. Apparent source blur sizes range between 1 nm and 3.5 µm, for emitter radii between 160 µm and 2.82 mm, as the current density increases from 1 to 1000 A/cm2. Such small aberrations imply that discrete space charge effects do not significantly degrade the performance of these electron sources under most conditions.

Photoelectric spectra of SnTe: structural similarity with PbTe and PbSe spectra

The results of the measurements of photoelectric spectra of SnTe excited with photons in the interval between 6.5 and 10 eV and of PbSe in the interval between 7.25 and 8.75 eV are presented. These results are discussed in detail in connection with published photoelectric spectra of PbTe, with available theoretical valence density of states of PbTe and PbSe and with available band schemes of the three substances. On the basis of the structural similarity of the spectra of these substances and of the combined analysis of these data, a correspondence scheme between the structures of the spectra of these substances is proposed and the origin of the main contributions to photoelectric structures is clarified.

Photoelectron spectroscopy of crystalline antimony: a comparison with SnTe spectra

The energy distribution curves of photoelectrons emitted by crystalline antimony excited with photons in the energy interval between 5.25 and 9.75 eV are presented. The comparison with the distribution curves of SnTe makes it possible to point out the photoelectric structures basically due to the structural similarity of the two compounds and the features typical of the semimetallic nature of antimony.