High-efficiency GaAs solar cells

An updated review of the state of the art in the development of GaAs solar cells is provided, with emphasis on AlGaAs-GaAs cells suitable for space applications. A set of theoretically derived characteristics is given for this type of solar cell. Comparison of measured performance with theory shows excellent agreement. Data on the effects of radiation damage (high-energy electrons, protons, and neutrons) is also integrated into a form useful for evaluation purposes. Techniques for fabricating (AlGa)As-GaAs solar cells in quantities large enough for practical applications are discussed and are shown to have been demonstrated. The possibility of extending these techniques to the fabrication of very thin low-weight cells for space applications is also considered. Finally, the results obtained to date in the development of GaAs solar cells for applications requiring concentrated sunlight are reviewed, for terrestrial as well as for space applications. As a milestone toward the practical application of AlGaAs-GaAs solar cells in space systems, a brief account is provided on the development status of small experimental AlGaAs-GaAs solar-cell panels for specific space flights.     

High-efficiency dual-junction GaInP/GaAs tandem solar cells obtained by the method of MOCVD

Monolithic dual-junction GaInP/GaAs solar cells grown by the MOCVD method were studied. The conditions of the growth of ternary Ga _x In_1?x P and Al _x In_1?x P alloys lattice-matched to GaAs are optimized. Technology for fabrication of a tunneling diode with a high peak current density of 207 A/cm² on the basis of heavily doped n ⁺⁺-GaAs:Si and p ⁺⁺-AlGaAs:C layers is developed. Cascade GaInP/GaAs solar cells obtained as a result of relevant studies featuring a good efficiency of the solar-energy conversion both for space and terrestrial applications. The maximum value of the GaInP/GaAs solar-cell efficiency was 30.03% (at AM1.5D, 40 suns).     

High-efficiency monolithic GaAs IMPATT diodes

Impedance-matching circuits were integrated on the same chip as the IMPATT diodes to produce monolithic impatt diodes for millimetre-wave applications. A drastic reduction of device-to-circuit parasitic elements was achieved by placing the external circuitry very close to the device. Oscillators fabricated in this fashion gave the highest efficiencies reported so far in the 30?35 GHz range with 28% conversion efficiency using hybrid-Read structures.     

High-efficiency W-band GaAs monolithic frequency multipliers

High efficiency monolithic frequency multipliers have been designed, fabricated, and tested in the W-band. In microwave monolithic integrated circuits (MMICs), transmission lines with various impedances are used not only to transfer the input and output signals, but also to match the impedances of active devices to those of the input and output ports, with open and/or short stubs. Thus, loss in the transmission lines is one of the major limiting factors on circuit efficiencies. This paper presents high-efficiency MMIC frequency doublers with a balanced pair of GaAs Schottky barrier planar diodes operating in the W-band. The geometries of transmission lines were optimized to reduce the loss and thus to improve the efficiency. The demonstrated efficiency of 36.1% is the highest efficiency reported for a diode-based MMIC frequency multiplier in the W-band.     

GaInP/GaAs/Ge叠层太阳电池的研制及其温度依赖性分析

利用MOCVD方法制备了GaInP/GaAs/Ge叠层太阳电池。测试了I-V特性,并测试分析了该电池性能在30℃至170℃温度范围内的变化情况。测试结果表明,随着温度的升高,短路电流密度略微增大,温度系数为9.8 (μA/cm2)/℃;开路电压以系数-5.6mV/℃急剧下降;填充因子也随之下降（-0.00063 /℃）;电池的转换效率随温度升高线性减小,温度从30℃升高至 130℃时,效率从28%下降至22.1%。最后,本文对该叠层电池随着温度变化的特性给予了详细的理论分析。     

High-efficiency AlGaAs/GaAs concentrator (2500 suns) solar cells

A study is made AlGaAs/GaAs heterostructure solar cells that have been optimized for ultrahigh concentrations of sunlight (1000–2500 suns). The maximum efficiencies were 25.1% at 500 suns, 25% at 1000 suns, and 22.8% at 2000 suns for sunlight passing through an air mass of AM1.5. Cells of this type open up the possibility of reducing the surface area of solar cells by more than three orders of magnitude and, as a result, substantially lowering the cost of electrical energy in power equipment with sunlight concentrators. Fiz. Tekh. Poluprovodn. 33, 1070–1072 (September 1999)     

Lightweight tandem GaAs/CuInSe2 solar cells

High-efficiency, ultralightweight, mechanically stacked 4-cm² thin-film tandem solar cells are discussed. The tandem stack consists of a single-crystal, thin-film Ga(Al)As cell fabricated by the cleavage of lateral epitaxy for transfer (CLEFT) process and adhesively bonded to the top of a CdZnS/CuInSe₂ polycrystalline thin-film cell deposited on glass. Maximum tandem efficiency in a four-terminal configuration of 21.6% AM0 have been demonstrated. This represents the highest thin-film cell efficiency reported to date. Individual subcells with efficiencies of 19.5% for CLEFT GaAs and 3.0% for CuInSe₂ have also been achieved. Cell specific power as high as 600 W/kg has been achieved with a 4-cm² cell weight of 188 mg without coverglass, at an efficiency of 20.8% AM0     

Over 35-percent efficient GaAs/GaSb tandem solar cells

The efficiency of GaAs solar cells can be substantially increased by locating an infrared-sensitive booster solar cell behind a transparent GaAs cell. Infrared-sensitive GaSb cells and visible-light-sensitive GaAS cells designed for use with concentrated sunlight are described. Prismatic cover slides are used to effectively eliminate grid shading losses for both the GaAs and the GaSb cells. With prismatic cover slides, the best component cell efficiencies add up to 38.2% under concentrated sunlight (100×AM1.5D). Two-terminal tandem cell circuit cards containing nine transparent GaAS cells and nine GaSb cells are also described. Without cell prismatic covers, circuit-level energy conversion efficiencies near 30% (AM1.5D) are demonstrated     

InAs量子点尺寸和间距对GaInP/GaAs/GaInAs/Ge多结叠层电池的影响

A metamorphic GaInP/GaAs/GaInAs/Ge multi-junction solar cell with InAs quantum dots is investigated, and the analytical expression of the energy conversion efficiency on the multi-junction tandem solar cell is derived using the detailed balance principle and the Kronig-Penney model.The influences of interdot distance, quantum-dot size and the intermediate band location on the energy conversion efficiency are studied.This shows that the maximum efficiency,as a function of quantum-dot size and distance,is about 60.15%under the maximum concentration for only one InAs/GaAs subcell,and is even up to 39.69%for the overall cell.In addition,other efficiency factors such as current mismatch,the formation of a quasicontinuum conduction band and concentrated light are examined.     

Recent progress in developing efficient monolithic all-perovskite tandem solar cells

Organic–inorganic halide perovskites have received widespread attention thanks to their strong light absorption,long carrier diffusion lengths,tunable bandgaps,and low temperature processing.Single-junction perovskite solar cells(PSCs)have achieved a boost of the power conversion efficiency(PCE)from 3.8%to 25.2%in just a decade.With the continuous growth of PCE in single-junction PSCs,exploiting of monolithic all-perovskite tandem solar cells is now an important strategy to go beyond the efficiency available in single-junction PSCs.In this review,we first introduce the structure and operation mechanism of monolithic all-perovskite tandem solar cell.We then summarize recent progress in monolithic all-perovskite tandem solar cells from the perspectives of different structural units in the device:tunnel recombination junction,wide-bandgap top subcell,and narrow-bandgap bottom subcell.Finally,we provide our insights into the challenges and scientific issues remaining in this rapidly developing research field.     

InGaP/GaAs/Ge triple‐junction solar cells with ZnO nanowires

ZnO nanowire (NW) grown on triple‐junction (TJ) solar cells via the hydrothermal growth method to enhance efficiency is investigated. In this paper, experimental results indicate that TJ solar cells with ZnO NW as an antireflection (AR) coating have the lowest reflectance in the short wavelength spectrum, as compared with those of bare TJ solar cells (without AR coating) and solar cells with SiN_x and TiO₂/Al₂O₃ AR coatings. ZnO NW has the lowest light reflection among all experimental samples, especially in the range of ultraviolet to green light (300–500 nm). It was found that ZnO NW could enhance the conversion efficiency by 6.92%, as compared with the conventional TJ solar cell. In contrast, SiN_x and TiO₂/Al₂O₃ AR coatings could only enhance the conversion efficiency by 3.72% and 6.46% increase, respectively. The encapsulated results also suggested that the cell with ZnO NW coating could provide the best solar cell performances. Furthermore, all samples are measured at tilt angles of 0°–90° and results show that the solar cells with ZnO NW have the highest efficiency at all tilt angles. Furthermore, a small NW diameter increases light absorption. Copyright © 2012 John Wiley & Sons, Ltd.     

大面积、高性能柔性 GaInP/GaAs/InGaAs叠层太阳电池的制备

柔性高效Ⅲ-Ⅴ族多结太阳电池正在被开发、应用于无人机、可穿戴设备和空间能源等领域.采用MOCVD技术在Ga As衬底上制备太阳电池外延层, 之后通过低温键合和外延层剥离方法将外延层转移到柔性衬底上.通过外延层剥离设备设计和大量参数优化实验, 实现了GaAs太阳电池结构从四英寸砷化镓晶圆上的有效分离, 且不产生缺陷并保持原有的性能.近期, 在50μm聚酰亚胺薄膜上制备的30 cm2大面积柔性GaInP/Ga As/InGaAs三结太阳电池实现了31. 5%的转换效率 (AM0光谱) , 其中开路电压3. 01 V, 短路电流密度16. 8 mA/cm2, 填充因子0. 845.由于采用了轻质的聚酰亚胺材料, 所得到的柔性太阳电池面密度仅为168. 5 g/m2, 比功率高达2 530 W/kg.     

Interface contribution to GaAs/Ge heterojunction solar cellefficiency

A solar cell formed by growing a p-on-n AlGaAs/GaAs heteroface homojunction on a thin Ge substrate is studied by investigating the contribution of the GaAs/Ge heterostructure to the solar-cell efficiency. The existence of interface states is required in the absence of a Ge p-n junction to produce the photovoltaic effect with an open-circuit voltage enhancement as experimentally observed. Dark current-voltage characteristics of the GaAs/Ge heterojunction are calculated when the carrier transport is by thermionic emission and tunneling mechanisms. The evaluations correctly explain the observed changes of efficiency, the decrease of fill factor, the increase of open-circuit voltage, and the insignificant change of short-circuit current as compared to a GaAs/GaAs solar cell. It the short-circuit current from the heterojunction is on the order of 25 mA/cm², which is less than that of the p-n junction cell, the reduction of the solar cell efficiency is about 0.5-1.5% over a wide range of GaAs/Ge doping concentrations. Very few interface states tend to yield a diode-like dark I-V curve     

Enhanced efficiency in GaInP/GaAs tandem solar cells using carbon doped GaAs in tunnel junction

Carbon doping of GaAs using CBr₄ (carbon tetrabromide) in metal-organic chemical vapor deposition (MOCVD) was investigated to obtain very high and sharp doping profiles required for tunnel junction in tandem solar cells. It was found that the hole concentration increased with decreasing growth temperature and V/III ratio. Hole doping profiles versus distance from the sample surface showed that the hole concentration near the surface was very low in comparison with that far below the surface. As a post-growth treatment, CBr₄ was supplied during the cool down process and produced almost constant hole concentration of 1 × 10²⁰ cm⁻³ regardless of the depth, when CBr₄ flow rate was 9.53 μmol/min. Based on these results, solar cells were fabricated using both carbon (C) and zinc (Zn) as a p-type dopant. It was shown that C doping exhibits higher efficiency and lower series resistance than those of Zn doping in GaInP/GaAs tandem solar cells.     

Characterization testing of Measat GaAs/Ge solar cell assemblies

The first commercial communications satellite with gallium arsenide on germanium (GaAs/Ge) solar arrays was launched in January 1996. The spacecraft, named Measat, was built by Hughes Space and Communications Company. The solar cell assemblies consisted of large-area GaAs/Ge cells supplied by Spectrolab Inc. with infrared reflecting (IRR) coverglass supplied by Pilkington Space Technology. A comprehensive characterization program was performed on the GaAs/Ge solar cell assemblies used on the Measat array. This program served two functions: first to establish the database needed to accurately predict on-orbit performance under a variety of conditions; and second, to demonstrate the ability of the solar cell assemblies to withstand all mission environments while still providing the required power at end-of-life. Characterization testing included: measurement of electrical performance parameters as a function of radiation exposure, temperature and angle of incident light; reverse bias stability; optical and thermal properties; mechanical strength tests, panel fabrication, humidity and thermal cycling environmental tests. The results provided a complete database enabling the design of the Measat solar array, and demonstrated that the GaAs/Ge cells meet the spacecraft requirements at end-of-life.     

Perovskite/organic tandem solar cells

<正>In recent years, the power conversion efficiency (PCE) for single-junction perovskite solar cells (PSCs)[1,2]has reached25.7%, approaching the Shockley-Queisser limit (S-Q limit). Further enhancing efficiency is challenging. Tandem solar cells offer an effective way to further increase the efficiency beyond S-Q limit. Currently, perovskite/silicon tandem solar cells(TSCs)[3-5] have achieved a PCE of 31.3%[6]. However,     

AlGaAs/GaAs superlattice solar cells

A theoretical model is performed to study the viability of the AlGaAs/GaAs superlattice solar cell (SLSC). Using the Transfer Matrix Method, the conditions for resonant tunneling are established for a particular SL geometry with variably spaced quantum wells. The effective density of states and the absorption coefficient are calculated to determinate the J–V characteristic. Radiative, non‐radiative, and interface recombination were evaluated from a modeled SLSC, and their values were compared with a multiple quantum well solar cell of the same aluminum composition. A discussion about the conditions, where SLSC performance overcomes that of a multiple quantum well solar cell, is addressed. Copyright © 2011 John Wiley & Sons, Ltd.     

Accelerated publication 30.2% efficient GaInP/GaAs monolithic two-terminal tandem concentrator cell

The Ga_0.5In_0.5P/GaAs monolithic two-terminal tandem cell has been adapted for concentrator operation. the adaptation involves changes in the grid design, top-cell base thickness and top-cell emitter thickness. the prototype concentrator device has demonstrated an efficiency exceeding 30% in the concentration range of 115-260 suns, making this the first two-terminal monolithic cell to exceed 30% efficiency.     

Design and optimization of a monolithic GaInP/GaInAs tandem solar cell

We have theoretically calculated the photovoltaic conversion efficiency of a monolithic dual-junction GaInP/GaInAs device,which can be experimentally fabricated on a binary GaAs substrate.By optimizing the bandgap combination of the considered structure,an improvement of conversion efficiency has been observed in comparison to the conventional GaInP_2/GaAs system.For the suggested bandgap combination 1.83 eV/1.335 eV,our calculation indicates that the attainable efficiency can be enhanced up to 40.45%(30...     

A monolithic three‐terminal GaInAsP/GaInAs tandem solar cell

We describe the design and performance of a three‐terminal tandem solar cell for low‐concentration terrestrial applications. Designed for operation under a GaAs filter, the tandem demonstrates cumulative conversion efficiencies of 10.2 and 11.9% at 1 sun and 45 suns, respectively, under the concentrated direct spectrum. The middle terminal is shared between the two subcells and allows them to be operated independently at their respective maximum power points. Copyright © 2009 John Wiley & Sons, Ltd.