Figure 3 - uploaded by Daniel Derkacs
Content may be subject to copyright.
Bi-facial process: grow InGaAs cell, flip wafer in reactor load lock, grow rest of cell. InGaAs illuminated through wafer.
Source publication
Spire Semiconductor has demonstrated a new bi-facial epigrowth manufacturing process for InGaP/GaAs/InGaAs N/P tandem concentrator cells. NREL has verified 1cm<sup>2</sup> cells as 41.0% efficient at 500X, and 5.5mm cells as 41.4% at 334X, AM1.5D, 25C, matching within measurement error the world record efficiency. A lattice-mismatched 0.94eV InGaAs...
Context in source publication
Context 1
... Ga 0.83 As/Ge metamorphic cells with 1.1% mismatch were made with efficiency up to 41.1% at 454X by Fraunhofer [3]. Another approach to achieve higher efficiency is to substitute lattice-mismatched InGaAs for the Ge bottom cell (a "Ge-free" approach). The inverted metamorphic (IMM) process ( Fig. 2 Spire Semiconductor's bifacial epigrowth process (Fig. 3) makes InGaP/GaAs/InGaAs tandems without using whole- area wafer bonding and epitaxial liftoff steps which are not standard III-V cell process steps and may be low yield. The dislocations of the lattice mismatched cell are isolated from affecting the middle and top cells on the opposite wafer side by the thick GaAs wafer. Also, no ...
Similar publications
We have investigated wide-bandgap, metamorphic GaAs1-xPx and InyGa1-yP solar cells on GaAs as potential subcell materials for future 4-6 junction devices. We identified and characterized morphological defects in tensile GaAs1-xPx graded buffers that lead to a local reduction in carrier collection and a global increase in threading dislocation densi...
Self-assembled In <sub>0.22</sub> Ga <sub>0.78</sub> As quantum dots (QDs) grown on Si substrate with Ge / Si Ge as buffer layer grown by metal organic vapor phase epitaxy were investigated. Transmission electron microscopy and atomic force microscopy images were used to observe the size and space distribution of the In <sub>0.22</sub> Ga <sub>0.78...
Self-assembled InAs quantum-dot lasers grown by molecular-beam epitaxy using an AlGaAsSb metamorphic buffer layer on a GaAs substrate are reported. The resulting quantum-dot ensemble has a density >3×1010/cm2 and a ground-state transition ranging from 1.46 to 1.63 μm. Pulsed, room-temperature operation generates lasing from the first excited state...
A photovoltaic conversion efficiency of 40.8% at 326 suns concentration is demonstrated in a monolithically grown, triple-junction III-V solar cell structure in which each active junction is composed of an alloy with a different lattice constant chosen to maximize the theoretical efficiency. The semiconductor structure was grown by organometallic v...
GaAsxP1−x graded buffers were grown via solid source molecular beam epitaxy (MBE) to enable the fabrication of wide-bandgap InyGa1−yP solar cells. Tensile-strained GaAsxP1−x buffers grown on GaAs using unoptimized conditions exhibited asymmetric strain relaxation along with formation of faceted trenches, 100–300 nm deep, running parallel to the [01...
Citations
... Higher efficiencies can be obtained by optimizing the bandgaps of all three subcells, in which the Ge bottom junction could be replaced with a 1.0 eV junction In 0.3 Ga 0.7 As-based subcell. In a typical 3J cell architecture, the InGaP/GaAs/InGaAs structure is epitaxially grown by molecular beam epitaxy (MBE) or MOCVD methods in an inverted order: on a GaAs substrate, lattice-matched top InGaP and bottom GaAs subcells are grown at first, followed by transparent graded-composition buffer layers, and finally a metamorphic 1 eV InGaAs bottom cell [39,40]. The GaAs substrate is subsequently removed via mechanical polishing and/or chemical wet etching and the thin-film device is bonded to a carrier substrate for the remaining processing steps. ...
This chapter reviews the recent progress of thin‐film III–V semiconductor‐ based PV technologies, specifically III–V solar cells integrated with flexible substrates. First, we discuss single junction and MJ III–V solar cells, and their operational principles for energy conversion and experimental process. Second, fabrication schemes and concepts to epitaxially release these thin‐film solar cells and integrate them with flexible platforms are overviewed, and their applications in various areas, e.g. energy production, aerospace, sensing, and healthcare, are also discussed. Finally, we present strategies to further improve solar cell performance by developing advanced device and system architectures. To summarize, these thin‐film flexible III–V solar cells and systems offer viable routes for energy supply in many emerging applications.
... In this direction, Gallium indium phosphide (GaInP 2 ) and Gallium arsenide (GaAs) have been extensively used as top and middle layer [1] and Germanium (Ge) as bottom layer [1,2] in different multijunction solar cells. Indium gallium arsenide (InGaAs) has also been used as the bottom layer instead of Ge layer [3]. Recently, another emerging III-V semiconductor alloy Gallium Arsenic Bismide (GaAs 1-x Bi x ) has attracted much attention due to its' suitable optoelectronic parameters such as bandgap, electron and hole mobility, doping concentrations etc. to realize high-efficiency multijunction solar cell [4][5][6][7][8][9]. ...
In this paper, an emerging material GaAs 1-x Bi x has been introduced in different layers of multijunction solar cells. By modifying the spectral p-n junction model, the theoretical efficiencies of two-, three-and four-junction III-V bismide multijunction solar cells have been estimated to be 36.5%, 44.0%, and 52.2% respectively for AM1.5G under 1 sun condition. The effects of the material bandgap, sun concentration, and surface recombination velocity on the cell performance have been studied extensively. Simulation results revealed that an increment up to ~10% on the overall cell efficiency can be achieved by concentrating the solar radiation from 1 sun to 500 sun; and a 3-4 % increment on the overall cell efficiency by tuning the bandgap of the bismide layer as well as modeling the surface recombination velocity involved. These simulation results could be utilized for better understanding the materials as well as in realization of highly efficient bismide based multijunction solar cells.
... 2005 yılında Michael Grätzel, %11.04 verimliliğe sahip boya sentezli güneş hücreleri üretmiştir [4]. 2010 yılında S.Wojtczuk ve grubu da, InGaP/GaAs/InGaAs yapısını kullanarak % 41 verimliliğe sahip güneş hücresi elde etmeyi başarmışlardır [5]. 2015 yılında Babar Hussain ve arkadaşları, modifiye edilmiş bir yazılım kullanarak, kristal p-tipi silisyum (p-Si) ve n-tipi çinko oksit (n-ZnO) malzemelerine dayanan tek heteroeklemli güneş hücresi modeli önermişler ve en iyi verimliliği %19 olarak öngörmüşlerdir [6]. ...
... Diğer taraftan, Tablo 1'de verilen güneş hücrelerinin verimlerinin, literatürdeki bir kısım güneş hücrelerinin verimlerine kıyasla, nispeten düşük olduğu görülmektedir [2][3][4][5][6][7][8]. Düşük verim, iki yarı iletken arasındaki tükenme bölgesindeki yüklerin yeniden birleşmesinden dolayı ya da gazların geçmesine izin verecek şekilde gözenekli bir yapıya sahip olan ZnO filminin yapısı nedeniyle olabilmektedir [26]. ...
Bu çalışmada, n-tipi çinko oksit/p-tipi silisyum (n-ZnO/p-Si) heteroeklem güneş hücresinin verimliliği üzerinde çinko oksit (ZnO) kaplama miktarının etkisi incelendi. ZnO nanoparçacıklar sol-jel yöntemi ile sentezlendi. Sentezlenen nanoparçacıklar, döndürerek kaplama metodu kullanılarak cam alttaşlar ve p-Si alttaşlar üzerine kaplandı. Kaplama işlemi, 2, 4, 5 ve 15 kat olarak farklı miktarlarda gerçekleştirildi. Kaplama işleminden sonra, ince film kaplı alttaşlar, kare bir fırın içerisine konuldu ve 500 oC de 30 dk tavlandı. Yapı karakterizasyonu ve yüzey morfolojisi, X-ışını kırınımı metodu (X-ray diffraction; XRD) ve taramalı elektron mikroskobu (scanning electron microscopy; SEM) kullanılarak analiz edildi. Her bir n-ZnO/p-Si heteroeklem güneş hücresi yapısı için, kısa devre akımı (Isc) ve açık devre voltajı (Voc) elektriksel ölçümler ile tespit edildi ve verimlilik (n) hesapları yapıldı. Tüm işlemler oda sıcaklığında gerçekleştirildi. Yapılan bu çalışmaya göre, güneş hücrelerinin verimi, kritik bir kalınlığa kadar, ZnO kaplama miktarının artışı ile artmakta, kritik kalınlık aşıldığında (daha fazla ZnO kaplama yapıldığında) da düşmektedir. Buradan, ZnO kaplama miktarının (ZnO tabaka kalınlığının) güneş hücrelerinin performansını etkileyen önemli bir parametre olduğu sonucuna varıldı.
... The AlGaAs/GaAs tunnel junction is a widely used structure in concentrator cells. This structure has been used in a number of record breaking concentrator cells [31][32][33]. This is mostly due to two significant advantages: AlGaAs can be more easily doped with carbon than GaAs (which at least partially compensates for the higher bandgap) and it also seems possible that the diffusion suppressing effect of a high aluminum content layer is operative in this structure. ...
Tunnel Junctions, as addressed in this review, are conductive, optically transparent semiconductor layers used to join different semiconductor materials in order to increase overall device efficiency. The first monolithic multi-junction solar cell was grown in 1980 at NCSU and utilized an AlGaAs/AlGaAs tunnel junction. In the last 4 decades both the development and analysis of tunnel junction structures and their application to multi-junction solar cells has resulted in significant performance gains. In this review we will first make note of significant studies of III-V tunnel junction materials and performance, then discuss their incorporation into cells and modeling of their characteristics. A Recent study implicating thermally activated compensation of highly doped semiconductors by native defects rather than dopant diffusion in tunnel junction thermal degradation will be discussed. AlGaAs/InGaP tunnel junctions, showing both high current capability and high transparency (high bandgap), are the current standard for space applications. Of significant note is a variant of this structure containing a quantum well interface showing the best performance to date. This has been studied by several groups and will be discussed at length in order to show a path to future improvements.
... There is an urgent need to research after new (High Concentration (concentration factor 300-1000 suns) Photovoltaic Systems i.e. III-V multi-Junction tandem cells or high multiple exciton generation nanoparticles with tunable optical gaps) or cheaper thin film technologies such as the Cu 2 ZnSn(S,Se) 4 (CZTS) quaternary semiconductor compound which has similar properties as CdTe and CIGS! [27][28][29][30][31][32][33][34][35][36][37] Fast SE-mapping by expanded beam ellipsometry ...
Non-destructive analyzing tools are needed at all stages of thin film photovoltaic (PV) development, and on production lines. In thin film PV, layer thicknesses, micro-structure, composition, layer optical properties, and their uniformity (because each elementary cell is connected electrically in series within a big panel) serve as an important starting point in the evaluation of the performance of the cell or module. An important focus is to express the dielectric functions of each component material in terms of a handful of wavelength independent parameters whose variation can cover all process variants of that material. With the resulting database, spectroscopic ellipsometry coupled with multilayer analysis can be developed for on-line point-by-point mapping and on-line line-by-line imaging. This work tries to review the investigations of different types of PV-layers (anti-reflective coating, transparent-conductive oxide (TCO), multi-diode-structure, absorber and window layers) showing the existing dielectric function databases for the thin film components of CdTe, CuInGaSe2, thin Si, and TCO layers. Off-line point-by-point mapping can be effective for characterization of non-uniformities in full scale PV panels in developing labs but it is slow in the on-line mode when only 15 points can be obtained (within 1 min) as a 120 cm long panel moves by the mapping station. In the last years [M. Fried et al., Thin Solid Films 519, 2730 (2011)], instrumentation was developed that provides a line image of spectroscopic ellipsometry (wl = 350-1000 nm) data. Up to now a single 30 point line image can be collected in 10 s over a 15 cm width of PV material. This year we are building a 30 and a 60 cm width expanded beam ellipsometer the speed of which will be increased by 10x. Then 1800 points can be mapped in a 1 min traverse of a 60 * 120 cm PV panel or flexible roll-to-roll substrate.
... In order to reach high efficiency full spectrum utilization must be achieved. This can be accomplished using multiple bandgap PV cells in combination with spectral management of the incident solar illumination [2][3][4] . Two approaches have been pursued to achieve this goal: 1) the use of full spectrum concentration and tandem filtering with multi-junction PV cells in series; and 2) spectrum splitting optics with multiple single junction PV cells. ...
Spectrum-splitting is a beneficial technique to increase the efficiency and reduce the cost of photovoltaic (PV) systems. This method divides the incident solar spectrum into spectral components that are spatially separated and directed to PV cells with matching spectral responsivity characteristics. This approach eliminates problems associated with current and lattice matching that must be maintained in tandem multi-junction systems. In this paper, a two-junction holographic spectrum-splitting photovoltaic system is demonstrated with a folded PV geometry. The system is designed to use both direct and diffuse solar irradiation. It consists of holographic elements, a wedge-shaped optical guide, and PV substrates with back reflectors. The holographic elements and back reflectors spatially separate the incident solar spectrum and project spectral components onto matching PV cell types. In addition, the wedge-shaped optical guide traps diffuse illumination inside the system to increase absorption. In this paper, the wedge spectrum splitting system is analyzed using tabulated data for InGaP2/GaAs cells with direct illumination combined with experimental data for reflection volume holograms. A system efficiency of 31.42% is obtained with experimental reflection hologram data. This efficiency is a 21.42% improvement over a similar system that uses one PV cell with the highest efficiency (GaAs). Simulation results show large acceptance angle for both in-plane and out-of plane directions. Simulation of the output power of the system with different configurations at different times of the year are also presented.
... Multijunction (MJ) cells used in concentrated photovoltaic (CPV) systems provide the highest electrical efficiencies achieved to date [1][2][3][4]. Because the MJ stack consists of a series connection of multiple subcells, its current is limited by the least generating subcell. ...
An indoor method is presented for the quantification of the current‐matching ratio of a multijunction cell within a concentrator under arbitrary spectral irradiance conditions. The cell current is measured across a very large spectral sweep to force the relevant subcells into a limiting condition. The light spectrum is monitored using component cells to avoid the need for a spectroradiometer and spectral response measurements. The method also provides an estimation of the current losses beyond the overall current mismatch, for example, losses produced in concentrators with chromatic aberration by the non‐uniformity of the incident spectrum across the cell. The method has been applied to a pair of refractive point‐focus concentrator systems; first, a 300X single‐stage Fresnel lens over a lattice‐matched GaInP/Ga(In)As/Ge triple‐junction cell and second, a 1000X two‐stage system with the same Fresnel lens over a homogenizing secondary lens that encapsulates a triple‐junction cell of the same kind but smaller. The experiment demonstrates that the single‐stage concentrator exhibits a higher sensitivity of the current mismatch to variations in the focal distance. Copyright © 2012 John Wiley & Sons, Ltd.
... Where L is the net diffusion length, L 0 is the diffusion length of defect free III-V material, N dis is the dislocation density present in solar cell, ∅ is the electron radiation fluence per cm 2 and KL is material dependent radiation constant [8]. Values of radiation constant have been found by fitting the degradation behavior of Jsc of different subcells in IMM [7]; given the thicknesses of IMM sub-cells [9] and doses of 1Mev equivalent electron fluence. Radiation constant obtained for GaInP, matches closely with other references [10,11] but since GaAs and InGaAs cells are beneath InGaP cell there is deviation in GaAs and InGaAs radiation constants. ...
... Considering 5% loss due to grid shadowing loss and reflection, AM0 efficiency of ~36% has been calculated. Thicknesses of solar cells also match experimentally fabricated devices [9,13]. More details on theoretical framework and comparison between experimental and modeled results can be found elsewhere [2,14]. ...
In this work we have evaluated thickness dependent efficiency of 4J-IMM solar cells as a function of radiation doses and dislocations. It's been shown that bottom 0.7ev InGaAs sub-cell's radiation resistance and/or dislocation tolerance can be improved by use of back gold reflection. Photon confinement results in fabrication of thinner sub-cells thus increasing the radiation hardness of the sub-cells. It's been shown that for moderate to high doses of radiation, very high EOL efficiencies can be afforded with substantially higher dislocation densities than those commonly perceived as acceptable for IMM devices i.e. even in the presence of dislocation densities in both sub-cells as large as 107 cm-2, for typical 1015 cm-2 1MeV electron fluence, a remaining power factor >85% (ηEOL~32%). These finding could in turn be used to simplify manufacturing (thinner graded buffers) or/and increase yield for IMM space cells and also explain the irregular radiation behavior seen in 4J-IMMs.
... For example, efficiency of 0.4 is achieved at concentration of 433 and temperature 921°C. This is comparable to the efficiencies reported for state of the art multi-junction cells at flux concentration of several hundred suns [9,10]. A possible advantage of the PETE converter's high operating temperature is the potential for adding a secondary thermal cycle leading to overall efficiencies higher than 0.5 [3]. ...
Photon Enhanced Thermionic Emission (PETE) is a recently proposed novel concept in solar energy conversion, combining thermal and photovoltaic carrier excitation with thermionic emission. A recent study has shown that PETE conversion efficiencies can theoretically rise above 40% at concentration of 1000 suns. We analyze two major aspects missing from previous treatment of PETE conversion efficiency: changes in the cathode's conduction band carrier concentration with the electrical operating point; and determination of the cathode temperature from a full thermal energy balance. The results show that the conversion efficiency is a monotonically increasing function of temperature, and a monotonically decreasing function of the cathode electron affinity. It is shown that PETE converter efficiency according to the modified model is higher than previously reported, but achieving very high efficiencies of over 40% requires high temperatures that may be difficult in practical implementation.
... 5,6 By introducing multiple energy thresholds, the limiting energy conversion efficiency of both organic 7−9 and inorganic solar cells can be increased, the latter type reaching efficiencies exceeding 40%. 10,11 However, these multijunction devices are inherently more complex and expensive to manufacture. Thin film solar cells, such as amorphous silicon 12 and in particular organic bulk heterojunction (OPV) 13,14 devices, potentially offer cheaper energy than commercially available crystalline silicon solar cells. ...
The efficiency of thin-film solar cells with large optical band gaps, such as organic bulk heterojunction or amorphous silicon solar cells, is limited by their inability to harvest the (infra)red part of the solar spectrum. Photochemical upconversion based on triplet–triplet annihilation (TTA-UC) can potentially boost those solar cells by absorbing sub-bandgap photons and coupling the upconverted light back into the solar cell in a spectral region that the cell can efficiently convert into electrical current. In the present study we augment two types of organic solar cells and one amorphous silicon (a-Si:H) solar cell with a TTA-upconverter, demonstrating a solar cell photocurrent increase of up to 0.2% under a moderate concentration (19 suns). The behavior of the organic solar cells, whose augmentation with an upconverting device is so-far unreported, is discussed in comparison to a-Si:H solar cells. Furthermore, on the basis of the TTA rate equations and optical simulations, we assess the potential of TTA-UC augmented solar cells and highlight a strategy for the realization of a device-relevant current increase by TTA-upconversion.
