Photoelectric Converters Research Articles

Quasistatic thermal and nonlinear processes of photoconversion of high-density optical radiation by multilayer structures

The results of the systematic experimental analysis of the thermal nonlinear electro-optic properties of photoelectric converters with silicon vertical cells in comparison with solar elements and elements on the basis of In/Ga/As are presented. The parameters of the linear and quadratic approximations for the investigated dependences are determined, that allows constructing a scalable analytic model of the converter with a given type of the working elements switching.

ANTI-REFLECTIVE PROPERTIES OF GRADIENT-POROUS SILICON

The theoretically achievable efficiency of the PEC for the single-cell solar cells (SC) is 30%. However, the cost of electricity generated by means of the solar cells has already become equal to that of natural gas. At the same time, the maximum confirmed efficiency for the solar cell is 26.3%. Thus, a certain lag behind the theoretically possible value is still observed. Analysis of the losses of modern photoelectric converters shows that at least 10% of them are related to the reflectivity of the SC surface. Therefore, along with intensive studies on heterojunction, thin-film constructive solutions, much attention is paid to other ones that allow for more than double the conversion efficiency. The paper deals with the formation of antireflective coatings on the surface of the PEC. One of the promising antireflection materials, which is widely studied at the present time, is porous silicon, called black silicon (black silicon b-Si) in the literature. The development of chemical and anodic silicon etching technologies, as well as the low cost and simplicity of the forming process, allow producing b-Si structures with controlled parameters of the antireflection layers. This paper presents the comparative results of the investigation of the reflection coefficients of various porous films obtained by anodic etching of the surface of silicon wafers with orientations (100) and (111). Experimental data indicate a significant decrease in the reflection coefficient in the visible light range from 400 to 1200 nm for all samples with porous layers compared to samples without porous layers. Especially noticeable is the decrease in the degree of reflection for the variational gradient-porous (GPSi-var) structures with a nano-porous outer layer. The magnitude of the reflection coefficient for such structures falls to the level of 0.1% in the range of the investigated frequencies of light radiation. For all porous layers, the tendency of decreasing the degree of reflection is typical as the wavelength of light decreases to less than 10% (compared to the reflection coefficient of the surface of silicon wafer at 30%).

Multifunctional Silicon Optoelectronics Integrated with Plasmonic Scattering Color.

Plasmonic scattering from metallic nanoparticles has been used for centuries to create the colorful appearance of stained glass. Besides their use as passive spectral filtering components, multifunctional optoelectronic applications can be achieved by integrating the nanoscatters with semiconductors that generate electricity using the complementary spectral components of plasmonic colors. To suppress the usual degradation of both efficiency and the gamut of plasmonic scattering coloration in highly asymmetric index configurations like a silicon host, aluminum nanodisks on indium tin oxide (ITO) coated silicon were experimentally studied and demonstrated color sorting in the full visible range along with photocurrent generation. Interestingly, the photocurrents were found to be comparable to the reference devices with only antireflection coatings in spite of the power loss for coloration. Detailed investigation shows that ITO serves as both the impedance matching layer for promoting the backward scattering and schottky contact with silicon, and moreover, plasmonic nanoscatters efficiently harvest the complement spectrum components for charge generation. The present approach combines the capacities of nanoscale color sorting and photoelectric converting at a negligible cost of efficiency, thus providing a broad flexibility of being utilized in various optoelectronic applications including self-powered display, filter-free imaging, and colorful photovoltaics.

Solar radiation concentrators paired with multijunction photoelectric converters in ground-based solar power plants (part I)

The present work is devoted to determining the conditions of the joint operation of photoelectric converter–solar concentrator pairs, which are used in solar power plants with concentrators. Three-cascade photoconverters based on A3B5 materials with different distributions of solar radiation in spectral ranges are studied. Concentrators of solar radiation are designed as the Fresnel lenses with silicon-on-glass structure. Refractive lens profile fabricated on the basis of Wacker RT604 silicone rubber is characterized by significant changes in refractive index with temperature. The effect of geometric parameters of the Fresnel lenses and their operating temperature on characteristics of solar radiation concentration in specified spectral intervals have been examined. The parameters of concentrators being paired with a photoelectric converter, which may ensure the efficient functioning of the solar power plant, have been calculated.

Photosensitive heterostructures based on porous nanocrystalline silicon

The features of the manufacturing process, as well as the results of studies on the morphology, electrophysical, and photoelectric properties of photosensitive structures based on silicon containing siliconcarbide and porous silicon layers, are considered. A porous layer is created on the surface of a monocrystalline silicon substrate via electrolytic etching in fluorine-containing solutions. Wafers with a different surface microrelief such as a ground, polished, and textured one, has been used. The carbonization of the samples resulting in the formation of SiC/Si heterostructures has been carried out via gas transport endotaxy in a hydrogen flow using a vertical reactor with cold walls and a graphite container. The structure and composition of the manufactured SiC/Si heterostructures formed on different types of structured surfaces on polycrystalline and monocrystalline silicon, including the surface porous silicon layer, are investigated. It is shown that the process of endotaxy on all the types of surfaces leads to the formation of a single-crystal phase of silicon carbide by cubic modification. Using scanning and transmission electron microscopy, the morphology of the produced structures is investigated. Filiform entities with a different structure have been revealed on nonporous surfaces identified as silicon carbide, whereas the cylindrical or conical structures, whose nature is uncertain, have been observed on porous surfaces. The current-voltage and current-power curves are plotted for all types of manufactured structures, the general form of which indicates the presence of several potential barriers there. The photoelectric properties of the structures and the prospects of their use in photoelectric converters of solar cells are analyzed.

Specific features of current flow mechanisms in the semiconductor structure of a photoelectric converter with an n +–p-junction and an antireflective porous silicon film

The temperature dependence of forward and reverse branches of the current–voltage characteristic of the semiconductor structure of a photoelectric converter with an n+–p-junction based on single-crystal silicon and an antireflective porous silicon film on the front surface has been studied. The presence of several current flow mechanisms has been revealed. It has been demonstrated that traps that emerge in the process of the formation of the porous silicon film have a considerable effect on the current flow processes in the semiconductor structure under consideration.

On the main photoelectric characteristics of three-junction InGaP/InGaAs/Ge solar cells in a broad temperature range (–197°C ≤ T ≤ +85°C)

This study is aimed at investigating the main photoelectric characteristics of three-cascade InGaP/InGaAs/Ge photoelectric converters in a broad temperature range (–197°C ≤ T ≤ +85°C). On account of analysis of photosensitivity spectra and optical current–voltage characteristics, such temperature dependences as the open-circuit voltage (V oc), filling factor of the current–voltage characteristic (FF), and the photoelectric conversion efficiency of solar radiation are determined. Investigations are performed at illumination intensities corresponding to operation under concentrated radiation. Decreased temperatures facilitate the selection of samples with the minimal “parasitic” potential barriers. The influence of excitationtransfer processes from a cascade into a cascade is estimated by means of secondary luminescent radiation. The highest photoelectric conversion efficiency of 52% is measured at a concentration multiplicity of 100 “suns” and a temperature of–160°C.

EXPERIMENTAL ASSESSMENT OF REFLECTION COEFFICIENT OF SILICON PHOTOELECTRIC CONVERTERS

Reflection is one of essential factors reducing the photoelectric converters overall performance therefore it was carried out an experimental assessment of the real loss of sunlight of the studied photoconverter. The analysis of experimental data showed that it is necessary to distinguish two types of reflection of a light stream from a working surface of the photoconverter. The paper deals with the special device which is designed and used in experiment. In this device, the studied sample is placed on the center in a framework in a form close to a hemisphere. This device allows to measure short circuit current of all battery at illumination of the studied sample through the calibrated opening in the top part of a framework. Silicon structures with the textured etching of a working surface (models of production of San Paulo, Brazil) possess the minimum integral reflection coefficient Kref = 8,3 %.

Photoelectric converters with quantum coherence.

Photon impingement is capable of liberating electrons in electronic devices and driving the electron flux from the lower chemical potential to higher chemical potential. Previous studies hinted that the thermodynamic efficiency of a nanosized photoelectric converter at maximum power is bounded by the Curzon-Ahlborn efficiency η_{CA}. In this study, we apply quantum effects to design a photoelectric converter based on a three-level quantum dot (QD) interacting with fermionic baths and photons. We show that, by adopting a pair of suitable degenerate states, quantum coherences induced by the couplings of QDs to sunlight and fermion baths can coexist steadily in nanoelectronic systems. Our analysis indicates that the efficiency at maximum power is no longer limited to η_{CA} through manipulation of carefully controlled quantum coherences.

Photovoltaic structures ITO/SiO х /n-Si of increased efficiency

Structures ITO/SiOх/n-Si are fabricated by pulverization of solutions of indium and tin chlorides on the (100) surface of silicon wafers with resistivity 4.5 Ω cm. The influence of the state of the Si surface on the efficiency of structures as photoelectric converters is investigated. It is shown that structures with an unetched surface of silicon wafers are the most efficient. Solar cells based on studied ITO/SiOх/n-Si structures with an inverse layer demonstrate an efficiency close to 16% in AM 1.5 conditions.

CALCULATION OF OPTIMUM PARAMETERS AND LIMIT CHARACTERISTICS OF CASCADE SILICON PHOTOCONVERTERS

Work is devoted to an assessment of optimum parameters of cascade silicon photo-electric converters. Unlike matrix solar elements the direction of a light stream is provided in cascade option perpendicular to the plane of several transitions created consistently on one basic plate of silicon. Follows from the analysis of constructive registration of the cascade photoconverter that the optimum mode of its work will be only when the solar light stream passing through basic layers of the semiconductor generates in them equal number of electron-hole couples in unit of time. This requirement can be realized by the corresponding calculation of extents of basic layers of the semiconductor. Thickness of high-alloyed layers n + and p + between basic layers have to be minimum and not exceed 0.5 microns everyone. Especially for determination of optimum values of basic layers in cascade silicon photoconverters settlement dependence of density of short circuit of silicon photo cells on semiconductor layer thickness at standard sunlight of AM-1.5 has importance. Calculations of optimum values of basic layers of cascade photoconverters are presented in work for two, three, four and five multitransitional structures. The analysis of parameters of multitransitional photoconverters allows to draw a conclusion that the considered semiconductor structures can be successfully used in devices of direct electrolysis of water on hydrogen and oxygen as the potential of such cascade photo cell lit with a sunlight considerably exceeds the potential of communication of atoms of hydrogen and oxygen in a water molecule. The same circumstance will help to take from sea water rich with minerals and other chemical elements which are of interest to certain industries and agriculture.

Solar cells with a charge pump: Theoretical prospects and technological aspects of the application

The initial results of the application of the concept of a charge swap in the structure of a photoelectric converter (PEC) are considered. The speed of the processes of separating and collecting photogenerated charge carriers in the traditional structure of silicon solar cells with charge pumps is analyzed. The charge pumps are local n+ regions in the Si-base of p-type conduction. An equivalent circuit is offered as a replacement overlay transistor. The experimental results of the influence of charge pumps on the light volt-ampere characteristic of solar cells are presented. The technological aspects forming the structure of a photoelectric converter with charge pumps are discussed.

Manufacturing technologies for photovoltaics and possible means of their development in Russia (Review): Part 2. Modification of production technologies for photoelectric converters, development of contact structures, and choice of promising technologies for expansion of FEC production in Russia

As the development of the first part of the review of modern industrial technologies for manufacture of photoelectric converters (PECs) of solar power, the present paper considers modifications of technologies for manufacture of PECs, including various thin-film techniques. Main tendencies in the advancement of contact structures of PECs are described. Formulation and substantiation are made for promising, in the authors' opinion, lines of the development of industry of PECs in Russia based on the upcoming implementation of 1.5 GW network photovoltaic power plants to 2020, which are developed with the national support under conditions of the fulfillment of rigid requirements to manufacture localization. As the most prospective technology for development of the competitive manufacture of photoelectric converters subject to the Russian scientific and engineering groundwork, the authors recommend the technology based on single-crystal silicon of the n type with the passivation of the frontal and rear sides and symmetrical contacts (n-PASHa), which provides the possibility to produce double-faced solar modules also.

Manufacturing technologies for photovoltaics and possible means of their development in Russia (Review). Part 1: General approach to the development of photoelectric converters and basic silicon technologies

The state and key tendencies of the development of basic technologies for manufacture of photoelectric converters (PECs) in the world are considered, and their advantages and disadvantages are discussed. The first part of the review gives short information on the development of photovoltaics in the world and planes of the development of solar power plants in Russia. Total power of photoelectric plants operating in various countries in 2015 exceeded 150 GW and increased in the last ten years with a rate of approximately 50% per year. Russia made important state decisions on the support of the development of renewable power engineering and developed mechanisms, which were attractive for business, on the stimulation of building of the network of solar power plants with a total power to 1.5 GW in the country to 2020. At the same time, the rigid demands are made with respect to the localization of the production of components of these plants that opens new abilities for the development of the domestic production of photovoltaics manufacture. Data on the efficiency of PECs of various types that are attained in the leading laboratories of the world are given. Particular emphasis has been placed on the consideration of basic silicon technologies of PEC manufacture, which had the widest commercial application. The basic methods for production of polycrystalline silicon and making single-crystal and multicrystal silicon are described. Fundamentals of making techniques for plates, PECs, and photoelectric modules based on single-crystal and polycrystalline silicon are considered. The second part will be devoted to modifications of manufacturing techniques for photoelectric converters, enhancement methods for contact structures, and recommendations of authors with respect to the choice of prospective technologies for the expansion of PEC production in Russia. It will involve formulations and substantiations of the most promising lines of the development of photoelectric converter production in Russia, based on the planned implementation of the network of solar power plants to 2020 with the national assistance under condition of the fulfillment of the rigid requirements to manufacture localization.

Comparative analysis of technical and economic parameters of different schemes of the electric power supply of autonomous desalination plants

This article reviews possible schemes of the power supply of an autonomous reverse osmosis desalination plant that uses a photoelectric converter as primary energy sources. Using the climate data of several regions that have a shortage of fresh water for drinking and technical purposes, a technical and economic evaluation of the use of solar energy for obtaining fresh water in regions with high levels of solar radiation was performed. The prospects of the partial or complete substitution of diesel fuel by energy derived from photoelectric converters in such systems for regions with a high level of insolation and cost of diesel fuel are shown.

Centering of the Screening Patterns and Code Wheels of Angular Movement Photoelectric Converters by Means of an Annular Hairline and Scale Lines

Methods of centering scanning patterns by means of a centering circle and scale lines are analyzed. It is shown that centering with respect to scale lines using two reading systems situated in diametrically opposite parts of the scanning pattern is the most accurate method.

Effect of Oligomer Structure on the Diffraction Efficiency of Holographic Recording Media

The development of new materials possessing photoconductance in the visible and near-IR regions holds great importance for the use of such materials in photoelectric solar energy converters, light emitters, light beam modulators and switches, and devices for recording, storage, and for the treatment of optical information. In addition to inorganic semiconductors, organic oligomers and their derived composites (OC) hold promise for practical application [1-8]. Most of the experience in the development of OC with hole-type conductance has been accumulated for electrographic and holographic information media [9-11]. These OC were tested in holographic recording media (HRM) for the photothermoplastic (PTP) method of recording optical information [12]. HRM for the PTP method of hologram recording should possess suitable rheological properties, high electrical resistance in the dark, and high photoconductance. Our studies over many years have indicated that the rheological properties are more important than photoconductance in the photosensitivity of the recoding layer of photothermoplastic material. Thus, the viscosity, surface tension, brittle temperature, and viscous flow activation energy are the major factors determining the photosensitivity of the oligomer films. The softening temperature and viscosity of oligomer photoconductors decrease with decreasing length of its main chain and increasing distance between bulky carbazolyl substituents. The presence of oxygen or silicon hinge atoms enhances the number of allowed conformations of the individual units, which permits lowering the softening temperature of the oligomer and increasing elasticity of the oligomer films. However, there is only sparse information in the literature on the effect of the shape oftheoligomermoleculesontheaboveproperties.Inthiswork,wecarriedoutacomparativestudyofthediffractionefficiency of holograms in HRM derived from linear and radial oligomers. The sensitivity of the recording layer of a photothermoplastic material is largely a function of the capacity of the oligomer photoconductor to undergo deformation upon the action of a surface charge. Since one of the factors inhibiting deformation is viscosity in the melt, a decrease in this viscosity should lead to a significant increase in the sensitivity of the recording layer. The distinguishing feature of radial, i.e., star-shaped, polymers is lower viscosity in melts and solutions relative to their linear analogs. This property led to the choice of radial siloxane oligomers for the creation of highly-sensitive HRM for the PTP method of hologram recording.

Bionics study on the MFD of human visual cells

Human visual cells are photon detectors and its outer segment is similar to optical fibers, so based on waveguide theory, in this research, the normalized frequency and mode field diameter (MFD) of human visual cell's outer segment were calculated and analyzed. For cone cells, wavelength data was sampled at 380nm, 419nm, 531nm, 559nm and 760nm; for rod cells wavelength data was sampled at 380nm, 498nm and 760nm. It was shown that the outer segment of cone cells works in single mode; for rod cells, its outer segment works as multimode. This analysis is referential to the bionics design of photoelectric converters which will meet the high requirement of optical communication in the near future.

Photoelectric converters in a system with spectral splitting of the solar energy

The results of modeling photoelectric converters in a system with spectral splitting of solar energy are detailed. The solar radiation in this system is divided into three spectral regions (Δλ1 725 nm) with the use of dichroic filters and is then converted into electric energy by the photoelectric converters based on single-junction InGaN/GaN and GaAs/AlGaAs heterostructures and monocrystalline c-Si silicon. Special attention is paid to the study regarding the possibility of expanding the spectral absorption range of the system by increasing the conversion efficiency in the ultraviolet part of the spectrum. The overall efficiency of the system in the entire spectrum varies from 21 to 37%, depending on the heterostructure design of the single-junction photoelectric converters and the configuration of the optical systems.

Development of a surface plasmon resonance biosensing approach for the rapid detection of porcine circovirus type2 in sample solutions.

A sensitive and label-free analytical approach for the detection of porcine circovirus type 2 (PCV2) instead of PCV2 antibody in serum sample was systematically investigated in this research based on surface plasmon resonance (SPR) with an establishment of special molecular identification membrane. The experimental device for constructing the biosensing analyzer is composed of an integrated biosensor, a home-made microfluidic module, and an electrical control circuit incorporated with a photoelectric converter. In order to detect the PCV2 using the surface plasmon resonance immunoassay, the mercaptopropionic acid has been used to bind the Au film in advance through the known form of the strong S-Au covalent bonds formed by the chemical radical of the mercaptopropionic acid and the Au film. PCV2 antibodies were bonded with the mercaptopropionic acid by covalent -CO-NH- amide bonding. For the purpose of evaluating the performance of this approach, the known concentrations of PCV2 Cap protein of 10 µg/mL, 7.5 µg/mL, 5 µg/mL, 2.5 µg/mL, 1 µg/mL, and 0.5 µg/mL were prepared by diluting with PBS successively and then the delta response units (ΔRUs) were measured individually. Using the data collected from the linear CCD array, the ΔRUs gave a linear response over a wide concentration range of standard known concentrations of PCV2 Cap protein with the R-Squared value of 0.99625. The theoretical limit of detection was calculated to be 0.04 µg/mL for the surface plasmon resonance biosensing approach. Correspondingly, the recovery rate ranged from 81.0% to 89.3% was obtained. In contrast to the PCV2 detection kits, this surface plasmon resonance biosensing system was validated through linearity, precision and recovery, which demonstrated that the surface plasmon resonance immunoassay is reliable and robust. It was concluded that the detection method which is associated with biomembrane properties is expected to contribute much to determine the PCV2 in sample solutions instead of PCV2 antibody in serum samples quantitatively.