AbstractWe have studied the possibility of creating laser-power converters based on LPE-grown InP(GaAs)/InP heterostructures intended for wireless power transmission via a laser beam channel at wavelengths λ ≈ 1.06–1.2 μm.

Laser-power converters for the wavelength λ = 808 nm are fabricated by liquid-phase epitaxy (LPE) on the basis of n-Al0.07GaAs–p-Al0.07GaAs–p-Al0.25GaAs single-junction heterostructures. The converters are tested with uniform (pulse simulator) and partly nonuniform (laser beam) illumination distribution over the photoreceiving surface. In the former case, a monochromatic efficiency of η = 53.1% is achieved for samples with an area of S = 4 cm2 at a power of 1.2 W. At S = 10.2 mm2 the efficiency is 58.3% at a laser power of 0.7 W.

Photovoltaic laser-power converters with irradiation of the substrate side are developed based on lattice-matched GaInAs/InP heterostructures formed by metal-organic vapor-phase epitaxy. Variants of antireflection coatings with a reflection minimum at a wavelength of λ = 1064 nm as well as features of chip bonding using soldering pastes with different melting points are considered. The efficiency of 34.5% (1.2 W, λ =1064 nm) is achieved for the converters with the area of 3.5 × 3.5 mm2 at uniform radiation conditions.

We have studied the possibility of creating laser-power converters based on LPE-grown InP(GaAs)/InP heterostructures intended for wireless power transmission via a laser beam channel at wavelengths λ ≈ 1.06–1.2 μm.

Фотоэлектрические преобразователи лазерного излучения (λ

AbstractLaser-power converters for the wavelength λ = 808 nm are fabricated by liquid-phase epitaxy (LPE) on the basis of n -Al_0.07GaAs– p -Al_0.07GaAs– p -Al_0.25GaAs single-junction heterostructures. The converters are tested with uniform (pulse simulator) and partly nonuniform (laser beam) illumination distribution over the photoreceiving surface. In the former case, a monochromatic efficiency of η = 53.1% is achieved for samples with an area of S = 4 cm^2 at a power of 1.2 W. At S = 10.2 mm^2 the efficiency is 58.3% at a laser power of 0.7 W.

На основе однопереходных гетероструктур AlGaAs/GaAs, полученных методом эпитаксии из жидкой фазы, созданы преобразователи лазерного излучения с длиной волны lambda=809 нм. Разработаны и протестированы фотоэлектрические модули с рабочим напряжением 4 В для преобразования излучения различной плотности. Исследованы два подхода --- без использования оптических концентрирующих систем и с применением линз Френеля. В фотоэлектрическом приемнике на основе 64 преобразователей лазерного излучения площадью 0.04 см2 и концентрирующей системы из матрицы кварцевых линз достигнут монохроматический кпд преобразования >44%. DOI: 10.21883/FTP.2017.05.44428.8427

Приведены сравнительные характеристики фотовольтаических преобразователей лазерного излучения на основе арсенида галлия с p-эмиттером, сформированным диффузией из газовой фазы в присутствии сурфактантов (изовалентных примесей) и без них. Показано, что использование индия и фосфора в процессе формирования p-n-перехода существенно влияет на характеристики полученных приборов. DOI: 10.21883/FTP.2017.05.44432.8477

The comparative characteristics of photovoltaic converters (of laser radiation) based on gallium arsenide with a p-type emitter formed by gas-phase diffusion in the presence of surfactants (isovalent impurities) and without them are reported. It is shown that the use of indium and phosphorus in the process of the formation of a p–n junction significantly affects the characteristics of the obtained devices.

This paper presents the technique of spectrum tuning in the multi-lamp solar simulator's workspace and accuracy (uncertainty) evaluation for measurement results of spectral irradiance in order to determine its suitability for GaInP/Ga(In)As/Ge multi junction solar cells testing has been performed.

Методом МОС-гидридной эпитаксии созданы метаморфные Ga0.76In0.24As-гетероструктуры фотопреобразователей на подложках n-GaAs. Обнаружено, что из-за разрыва валентных зон на гетерогранице p-In0.24Al0.76As /p-In0.24Ga0.76As (широкозонное окно/эмиттер) возникает потенциальный барьер для дырок вследствие технологической сложности создания высокой концентрации активной примеси в широкозонном материале. Использование четверного твердого раствора InAlGaAs c содержанием Al <40% позволило повысить концентрацию акцепторов в широкозонном окне до ~9·1018 см-3 и полностью нивелировать потенциальный барьер, тем самым уменьшив последовательное сопротивление прибора. Произведен расчет параметров метаморфного буфера GaInAs со ступенчатым профилем изменения содержания In, и оптимизированы параметры его эпитаксиального роста, что позволило улучшить собирание носителей заряда из области n-GaInAs и получить квантовую эффективность фотоответа на длине волны 1064 нм 83%. Фотопреобразователи, созданные на основе метаморфных гетероструктур с оптимизированными слоями широкозонного окна и метаморфного буфера, имели кпд преобразования излучения с длиной волны 1064 нм на уровне 38.5%. DOI: 10.21883/FTP.2017.01.8288

Laser-power converters with a wavelength of λ = 809 nm are fabricated on the basis of single-junction AlGaAs/GaAs heterostructures grown by the method of liquid-phase epitaxy (LPE). Photovoltaic modules with an operating voltage of 4 V for converting radiation of various densities are developed and tested. Two approaches—without the use of optical concentrating systems and with the use of Fresnel lenses are investigated. A monochromatic conversion efficiency exceeding 44% is attained with a photovoltaic module based on 64 laser-radiation converters 0.04 cm2 in area and a concentrating system made of a quartz-lens matrix.

Metamorphic Ga0.76In0.24As heterostructures for photovoltaic converters are grown by the MOCVD (metal–organic chemical vapor deposition) technique. It is found that, due to the valence-band offset at the p-In0.24Al0.76As/p-In0.24Ga0.76As (wide-gap window/emitter) heterointerface, a potential barrier for holes arises as a result of a low carrier concentration in the wide-gap material. The use of an InAlGaAs solid solution with an Al content lower than 40% makes it possible to raise the hole concentration in the widegap window up ~9 × 1018 cm–3 and completely remove the potential barrier, thereby reducing the series resistance of the device. The parameters of an GaInAs metamorphic buffer layer with a stepwise In content profile are calculated and its epitaxial growth conditions are optimized, which improves carrier collection from the n-GaInAs base region and provides a quantum efficiency of 83% at a wavelength of 1064 nm. Optimization of the metamorphic heterostructure of the photovoltaic converter results in that its conversion efficiency for laser light with a wavelength of 1064 nm is 38.5%.

Photovoltaic converters of laser light with a wavelength of λ = 1550 nm are developed using liquidphase epitaxy (LPE), metal-organic chemical-vapor deposition (MOCVD), and diffusion from the gas phase into the n-GaSb substrate. Photocells with an area of S of 4, 12.2, and 100 mm2 are fabricated and tested. The characteristics of the samples produced by different methods are compared. The monochromatic efficiency is found to be 38.7% for the best converters (with S = 12.2 mm2) at a laser power of 1.4 W.

The phenomenon of current spreading is essential for concentrator solar cells since it limits the conversion efficiency at high sunlight-concentration ratios. A model, which describes the regularities of the above phenomenon, is proposed and developed. The model uses a stylized representation of current lines and, respectively, of current tubes; it includes two resistive parameters accounting for the variable lateral (horizontal) component and the constant vertical component of the resistance of each tube. In the model the fact that the thickness of the spreading region is much less than the distance between the contact grid strips is taken into account. The calculated current—voltage (I–V) characteristics of a solar cell in the resistive and a nonresistive cases are obtained. The spreading-resistance I–V characteristic obtained by the voltage subtraction of these characteristics is nonlinear and depends on the photogenerated current. Thus, the equivalent electrical circuit of a solar cell includes a lumped nonlinear resistance, which depends parametrically on the photogenerated current. The comparison of experimental and calculated I–V characteristics by the example of Ge, GaAs, and GaInP solar cells is performed and both resistive parameters of the model are determined. The model describes correctly the regularities of spreading in single-junction solar cells and can be extended to multijunction solar cells.

A method is proposed for estimating the potential efficiency which can be achieved in an initially unbalanced multijunction solar cell by the mutual convergence of photogenerated currents: to extract this current from a relatively narrow band-gap cell and to add it to a relatively wide-gap cell. It is already known that the properties facilitating relative convergence are inherent to such objects as bound excitons, quantum dots, donor-acceptor pairs, and others located in relatively wide-gap cells. In fact, the proposed method is reduced to the problem of obtaining such a required light current-voltage (I–V) characteristic which corresponds to the equality of all photogenerated short-circuit currents. Two methods for obtaining the required light I–V characteristic are used. The first one is selection of the spectral composition of the radiation incident on the multijunction solar cell from an illuminator. The second method is a double shift of the dark I–V characteristic: a current shift J g (common set photogenerated current) and a voltage shift (−J g R s ), where R s is the series resistance. For the light and dark I–V characteristics, a general analytical expression is derived, which considers the effect of so-called luminescence coupling in multijunction solar cells. The experimental I–V characteristics are compared with the calculated ones for a three-junction InGaP/GaAs/Ge solar cell with R s = 0.019 Ω cm2 and a maximum factual efficiency of 36.9%. Its maximum potential efficiency is estimated as 41.2%.

The photovoltaic (PV) laser-power converters for the wavelength λ = 1550 nm have been produced by diffusion from the gas phase into an n -GaSb substrate. PV cells with areas of S = 4, 12.2, and 100 mm 2 have been fabricated and tested under a Xe flash lamp. The monochromatic (λ = 1550 nm) efficiency η = 34.8% is reached on the best samples with S = 12.2 mm 2 at a current density of 8 A/cm 2 . The stability of laser power converter and its degradation rate have been estimated at the operation temperature of 120°C.

The thermally induced degradation (temperature T ≈ 200°C) of Cr-Au, Cr-Au-Ag-Au, Ti-Pt-Au, and Ti-Pt-Ag contact systems deposited onto the surface of p -GaSb by magnetron sputtering and resistive evaporation are studied. It is found that photovoltaic (PV) converters with a contact grid based on Ti-Pt-Ag are characterized by the maximum thermal stability. PV cells with gold-containing contacts based on Cr-Au and Ti-Pt-Au exhibit a high rate of degradation with increasing temperature, which may require a more effective heat removal system for their operation.