The chapter will introduce industrial silicon solar cell manufacturing technologies with its current status. To learn about our use of cookies and how you can manage your cookie settings, please see our Cookie Policy. (a) Photogeneration profile of a 10-µm thick c-Si solar cell with Gaussian disorder, described by the RMS deviation of height σ=300 nm and the lateral correlation length lc = 160 nm. The electronic grade Si is generally 99.99% pure. Considering the case of silicon material, an important clarification has to be made here. In the Lambertian limit, the spectrally resolved photogeneration rate profile of the excited electron-hole pairs is given in closed form as [27]: (2) gLL(z,E)=αLLRbe−2αLLdeαLLz+e−αLLz1−Rbe−2αLLd1−1n2ϕAM1.5(E)(2). 264687 ‘PROPHET’. An atom of sili­con has 14 electrons, arranged in three different shells. Solar cells based on noncrystalline (amorphous or micro-crystalline) silicon fall among the class of thin-film devices, i.e. Nous proposons des milliers de produits dans toutes les catégories de vente, afin de satisfaire toutes vos envies. A properly designed solar cell has to be optically thick (i.e. All lengths are in µm. Figure 7. the integrated absorptance weighted with the solar spectrum – approaches the maximum value for thicknesses larger than several 10 µm. for more information on common third party cookies used for targeted marketing. Postdoc Ashley Morishige prepares to use a halogen lamp to “light-soak” a silicon wafer extracted from a PERC solar cell. Please specify the type of solar system you want quotes for. Run and results. The optimal values of silicon thicknesses – for material parameters that correspond to non-wafer-based silicon – lie in the range 20–100 µm, depending on material quality. Understand the simulation workflow and key results Modeling a solar cell typically requires both optical and electrical simulations. KAUST researchers have devised a way to turn rigid silicon into solar cells that can be stretched by a record-breaking 95 percent, while retaining high solar energy capture efficiency of 19 percent. To address this issue, the silicon in a solar cell has impurities-- other atoms purposefully mixed in with the silicon atoms -- which changes the way things work a bit. The former, called It should first be noticed that Jsc increases with increasing thickness because of improved absorption, while Voc increases with decreasing thickness thanks to improved current collection. This value can be compared with the detailed-balance limit for an unconstrained two-cell tandem, which is 45.7% [107,108]. In the last 5 years, exciting progress has been made with so-called perovskite solar cells, which are usually based on the methylammonium-lead-halide (MALI) material with a perovskite structure [105,106]. Silicon dominates the world of solar power. [18]. Please enter your e-mail (e.g. The current industrial standard for wafer-based silicon solar cells is 180 µm [8]. “We can get rid of the silicon … Nevertheless, it should be said that silicon solar cells must be very close to ideal conditions for the high-injection regime to occur. Become an affiliate, Opening Hours Instead, the silicon is melted and poured into a square mould, hence the square shape of polycrystalline. Carrier dynamics is modeled under the assumption of the depletion region approximation [25]. The diffusion lengths related to SRH recombination are LB = 232 µm for electrons in the p-type base [90], and LE = 23.2 µm for holes in the n-type emitter [25]. We and our partners use cookies on our website to improve your browsing experience, personalize content and ads, provide social media features, and analyze our traffic. Press release - researchmoz.us - Crystalline Silicon Solar Cells Market Statistics and Research Analysis Detailed in Latest Research Report 2020-2026 - published on openPR.com Livraison rapide Produits de qualité à petits prix Aliexpress : Achetez malin, vivez mieux SOLAR BATTERY CHARGING. We take the intrinsic carrier concentration equal to ni=9.65⋅109cm−3 [101]. Schematic geometry of (a) a solar cell with a single layer leading to single-pass absorption or (b) a layer with a Lambertian scatterer in the front and a back reflector in the rear side, leading to Lambertian light trapping; (c) short-circuit current density Jsc for c-Si, a-Si:H, GaAs, and CIGS (taking x=0.08) as a function of thickness, under AM1.5 solar spectrum. the two solar cells are assumed to be electrically independent. Monday - Thursday: 8:00am - 7:00pm Results are calculated with the finite-element method. Another possibility for improving upon the efficiency of single-junction silicon solar cells is that of III-V/silicon multijunctions. The maximum efficiency may occur under high-injection conditions, i.e. The electrical problem (i.e. Monocrystalline Silicon Solar Cells. The ARC and silver layers serve as front and back contacts, respectively. Standard silicon solar cell 1. As a consequence, the conversion efficiency has a broad maximum ∼20.3% for a thickness in the 10–50 µm range (the experimental value is 19% for a 43-µm thick cell [90]). You will receive up to four quotes tailored to your needs. Would you like to be part of GreenMatch? For the case of minority carriers in the base region, the diffusion equation under illumination may be written as: (4) DBd2ΔnBdz2−ΔnBτB+g(z,E)=0(4). Effect of surface recombination, expressed by the surface recombination velocity S at the rear surface, for different absorber thicknesses. Chapin now felt it was the time to introduce them to his employees at Bell telephone system and most of all to the world. Download figure; Open in new tab; Download powerPoint; 8. Prospects for overcoming the 29% limit by means of silicon/perovskite tandems are briefly discussed. (a) Energy conversion efficiency for solar cells with perfect surface passivation (SB = SE = 0 cm/s) as a function of the electron diffusion length in the base LB (with LE = 23.2 µm) and of the cell thickness. The general issue of light-trapping limits in micron-sized absorbing layers has been addressed in a number of papers [79–84], for a recent reassessment on this debated problem see Ref. Perovskite-silicon solar cell combination helps researchers achieve high efficiency in photovoltaic power generation. (b) Structure considered in the FEM simulations. 4.62 out of 5 $ 0.49 $ 0.30. The solution of drift-diffusion equation in 1-D by the generalized Hovel model is described in the next section. In this example, we will study a pillar silicon solar cell design where both the optical and electrical simulations of the device have to be carried out in 3D. However, under normal (experimentally realized) conditions, the generalized Hovel model gives a very good description of silicon solar cells as a function of thickness, including the effects of bulk and surface recombinations. However, the technology is new, and efficiency rates are thought to increase with technological breakthroughs in the near future. Silicon photovoltaic modules comprise ~90% of the photovoltaic modules manufactured and sold worldwide. When considering light trapping in a wide range of thickness, say from ~1 to 200 µm, it is important to employ optical structures whose design is weakly dependent on thickness. Usually, solar cells have a metal back reflector (BR) characterized by high reflectivity and low loss, which nearly doubles the optical path of light. It is widely used in pocket calculators, but it also powers some private homes, buildings, and remote facilities. 6–8 This review retraces recent advances in silicon solar cell technology towards that goal. The ingot materials are subsequently sliced into silicon wafers suitable for solar cell … This enhancement factor can also be related to the increase of the optical density of states within the absorbing layer that results from total internal reflection [16]. Monocrystalline solar cells, also called "single crystalline" cells are easily recognizable by their coloring. Scientists have set a new efficiency record for perovskite-silicon solar cells. Yet, these are incremental improvements on the line of the existing technology of single-junction solar cells, and they are eventually bound by the ~29% limit. Read more about our cookie policy. They were the first of commercially available solar cell technology. Achetez et téléchargez ebook Silicon Solar Cell Process Development, Fabrication and Analysis (English Edition): Boutique Kindle - Science : Amazon.fr National lockdown Installations can continue under all tiers. Recommended articles lists articles that we recommend and is powered by our AI driven recommendation engine. We show in this work that the range of thicknesses 20–100 µm is very interesting for solar cell performance, as it may lead to conversion efficiencies that exceed those of wafer-based silicon solar cells in realistic cases. Simulation setup Structures Figure 9. solar cells with a thickness of the order of a micron (200–300 nm for a-Si, ~2 µm for microcrystalline silicon). Thermodynamic and detailed balance calculations are provided to derive guideline for the optimization of perovskite solar cells. $17.99 $ 17. We include only intrinsic Auger recombination, and assume no Shockley–Read–Hall or surface recombination. Results are calculated with the generalized Hovel model. the collection of photogenerated carriers), we have discussed three different approaches, namely the ideal diode equation, an analytic model for solving drift-diffusion equations in 1-D (the generalized Hovel model), and full device simulations with the FEM. AOSHIKE 50pcs Solar Cells for Solar Panels Polycrystalline Silicon Micro Mini Solar Panel Cell DIY Charger Battery 0.5V 0.5A 78x19mm/3x0.75inches . However, you can change your cookie settings at any time at the bottom of this page. [6], the relative efficiency reduction of ~10% is attributed to a 5.3% reduction in FF, a 3.4% reduction in Jsc, and a 1.1% reduction in Voc. [98], with permission from IOP Publishing. Our customer service team reviews your request. Introduction Earlier Solar cells were used in spacecrafts. Actually the production costs of solar cells and modules have decreased to such an extent that the solar cell impacts for a fraction of the total cost, while more than 50% is due to electrical and other components (balance of system) and to indirect costs like installation, maintenance, insurance, financing. These two requirements lead to an optimal thickness that maximizes the efficiency. Breakthrough improvements with silicon tandems are more prospective and are still the focus of intense lab research. Next, we study the effect of extrinsic recombination. Efficiency and Solar Cell Cost Under laboratory conditions and with current state-of-the-art technology, it is possible to produce single crystal silicon solar cells close to 25% efficient. 125mm Mono Solar cells ,Sunpower, 2BB, 3.2W/PCS, 80,000pcs Summary of Solar Cell Production, and Limiting Efficiency of Silicon Solar Cell. In this model, which was first formulated in Ref. Under illumination, the carrier density increases and Auger recombination starts to contribute to the lifetime, thus an effective diffusion length can be defined as well. Your privacy is important to us. Recently, a III-V/Si triple-junction solar cell with 30.2% efficiency has been fabricated by means of wafer bonding of two independently prepared c-Si and GaInP/Al xGa 1−xAs solar cells [111]. The silicon pillars are radially doped and a 2D electrical simulation would not be sufficient for modeling the behaviour of the device. Our main goal is to understand realistic efficiency limits and prospects for thin-film c-Si solar cells produced with non-wafer-based techniques like layer transfer or liquid-phase recrystallization [90–95], which are needed for thicknesses below the wafer limit of ~80 µm. In this regime, surface texturization approaching the Lambertian limit of light trapping is commonly achieved with random pyramids, which are easily obtained via chemical etching of the silicon surface [25,26]. The record efficiency rose to 25.6% in 2014 [5] and to 26.7% in 2017 [6,7] thanks to the heterojunction (HJ) intrinsic thin layer technology based on thin a-Si passivating layers and on interdigitated back contacts (IBCs) on n-type silicon wafers. The cheaper alternative is polycrystalline or film cells. Effect of Shockley–Read–Hall recombination, expressed by the diffusion length, LB, for different absorber thicknesses. [85]. [99]) extends the validity of the treatment to the high-injection regime, when MB becomes larger than the doping. In Section 3, we discuss full electro-optical calculations for selected photonic and solar cell structures. It can first be seen that the photocurrent calculated with single-pass absorption is quite low for silicon, due to its indirect bandgap, unless the thickness exceeds several tens of microns. The following is a list of the third parties we collaborate with and a link to where you can opt opt of their personalised marketing programmes that we and other advertisers are using. In the past, amorphous solar cells were used for smaller-scale applications, such as pocket calculators, because their power output was relatively low. The Targray Solar Division commercializes a range of silicon materials for PV manufacturers and distributors. 5 inch Monocrystalline Solar cell. The word 'amorphous' literally means shapeless. For direct bandgap materials, on the other hand, a few microns are already sufficient to yield full absorption and the maximum photocurrent. It can be seen that both Voc and FF are strongly affected by surface recombination, even at values below S = 1 cm/s. In Section 2, we briefly review the problem of light trapping in solar cells, with emphasis on the so-called Lambertian limit that is obtained in the presence of a scatterer that randomizes the optical path of light. While costs associated with cell processing typically account for less than 20% of the total module cost and only about 10% at the system level, 5 increasing the power conversion efficiency of the solar cell offers a direct pathway to further reducing the levelized cost of electricity (LCOE). For the case of silicon, which has an indirect bandgap at 1.12 eV and long radiative recombination lifetimes, nonradiative Auger recombination of electron-hole pairs strongly limits the radiative efficiency and reduces the maximum conversion efficiency to about 29% [10,11]. In this section, we have shown that modeling c-Si solar cells with photonic light trapping requires proper merging of optical and electrical simulations. Top Produit Silicon Solar Cell for Panel pas cher sur Aliexpress France ! In 1954 the first solar cell battery was shown at a press conference powering a radiobroadcast. Notice that the silicon curves differ from those published in Ref. Heterojunction or HJT solar cells generaly use a base of high-purity N-type crystalline silicon with additional thin film layers of amorphous silicon on either side of the cell forming what is known as the heterojunction. Since 2005, our PV product portfolio has been a trusted source for high-purity polysilicon, solar silicon wafers, cells and ingots, and adhesive pastes for photovoltaics technology developers around the world. Efficiency limits with Lambertian light trapping, 88.40.hj Efficiency and performance of solar cells, numerical simulation 42.25.Bs Wave propagation, https://doi.org/10.1080/23746149.2018.1548305, https://www.ise.fraunhofer.de/en/publications/studies/photovoltaics-report.html, https://ec.europa.eu/jrc/en/publication/eur-scientific-and-technical-research-reports/pv-status-report-2017, https://www.silvaco.com/products/tcad/device.simulation/atlas/atlas.html. Boron doped emitters prepared by thermal diffusion using boron trichloride (BCl3) have been adopted in N-type Tunnel Oxide Passivated Contact (TOPCon) silicon solar cells. automated calls) and/or SMS with details or quotes for your enquiry and such products, and/or to confirm your product requirements. where ΔnB denotes the excess carrier concentration, DB is the diffusion constant, and τB is the effective lifetime of minority carriers. We have studied the efficiency limits by comparing the results of three different models, here listed in order of increasing complexity: In this model, the J-V characteristic of the solar cell is given by (3) J(V)=Jsc−qdR(V)(3). The generalized Hovel model (as well as the ideal diode equation approach) can still be used in the presence of surface recombination, but only in the most common regime of low injection, when the concentration of photogenerated carriers remains lower than the doping in the base (typically around 1016 cm−3). The P – type material should be thin so that light energy (EM radiation) will be able to penetrate the junction and reach the N – type material to allow diffusion of electrons and holes. The efficiency of wafer-based silicon modules has reached 24.4% and is constantly rising both in the lab and in the market. 99. This is usually called the regime of photonic light trapping and it can be realized with structures that are either periodic (diffraction gratings or photonic crystals [23,28–51]), modulated or aperiodic [52–55], disordered [56–69], quasi-random or with correlated disorder [70–72]. Also, we briefly mention how the 29% efficiency limit can be potentially overcome by the use of tandem structures employing the recently discovered perovskite solar cells. The optimal crystalline silicon (c-Si) thickness is calculated to be ~100 µm. (b) Scheme of the solar cell structure for the three models, including front and back contacts (serving also as ARC and back reflector, respectively) and the Lambertian scattering layer. In the last few years, much interest and intense research has been focused on the problem of light trapping in thin-film solar cells in the wave-optics limit, i.e. The triangles indicate the parameters of the record silicon solar cell with 26.3% efficiency [6]. Electro-optical modeling for thin-film silicon solar cells, 4. [98], with permission from IOP Publishing. In this simplified model, a p-n junction does not explicitly appear, although it has still to be considered in order to quantify the effect of Auger recombination. In this way, electricity is generated. Scientists have set the current world record of 29.15% efficiency for a tandem solar cell made of perovskite and silicon. We have studied another kind of texturization, namely a randomly rough interface with Gaussian disorder [59,60], whose design is also thickness independent to a large extent. In the following section, we shall present examples of full electro-optical calculations of solar cells incorporating this kind of thickness-independent roughness. Our results are based on theoretical models with different levels of complexity: in particular, we compare the results of analytic treatments with those of full device simulations that employ numerical solutions of the transport equations. Back in the days, silicon solar panels used to be rather expensive, as very high-quality silicon was required for creating them. The detailed procedure is described in Ref. The solar cell model is comprised of a 1D Si p-n junction that includes a Shockley-Read-Hall recombination and carrier generation. Such effects were often investigated using a simplified model based on the ideal diode equation [10,12–14]. [110]. solar_silicon_pillar.ldev. Become a Partner The efficiency limits of c-Si solar cells can be calculated by assuming Lambertian light trapping and by neglecting defect-related recombinations. The photogeneration profile is integrated over the spectral interval from 1.1 to 4.2 eV and averaged over both polarizations. 4.78 out of 5 $ 79.95 $ 55.00. We strive to connect our customers with the right product and supplier. Includes Auger, SRH, and ϕAM1.5 is the refractive index, and also maintain efficient charge carrier transport SE... [ 19,24 ] and we also include bandgap narrowing [ 97 ] are optimized for use in space IBCs a. Simulation setup structures the chapter will introduce industrial silicon solar cells the open-circuit voltage and maximum... Dominated the photovoltaic market since the very beginning in the next section bandgap,... The front interface, a 2-D surface roughness leads to a completely unordered amorphous structure with several varieties... To as “ 9N ” for “ 9 nines ”, a few microns are sufficient... Solar sign lighting system found our content valuable, feel free to give you the best browsing experience a. Layers serve as front and back contacts, respectively all to the electrodes the! Site to work such thin-film c-Si solar cells based on amorphous/microcrystalline silicon are running out of the silicon/perovskite tandem cell. Of their bulk ( wafer-based ) counterparts makes them most unique is that are! Updates, you are happy to receive all cookies on this website their dark black.... Denotes the excess minority carrier density in the market for more information on how to disable cookies in browser. Generated at a reasonable cost 8 ] electrically independent, but perovskites are certainly promising alternatives to the electrode of. Silicon ) called solar cells and kits to students silicon solar cell to learn about our use of and. And lower quality silicon prospective and are still fairly expensive, in to... Will receive up to £10,000 Vouchers, https: //www.linkedin.com/psettings/advertising review retraces advances... About renewable energy post oil crisis because of war between Arab and Israel panels used to track habits. ) amorphous silicon solar cells cells do not undergo the cutting process used monocrystalline. Million silicon atoms a second solar cell structure that is never approached in practice 2D simulation. To describe the transport of carriers as hardly any silicon is not structured crystallised... Prospective and are in good agreement with the Crossref icon will Open new... From 29.2 % to 25 % and it occurs for 80-µm thickness, with permission from IOP Publishing recommend. Of thin-film devices, i.e with IBCs with a wide bandgap and also surface recombination velocity at. Cells were made from thin slices or wafers cut from a PERC solar cell that. The integrated absorptance weighted with the full simulations strongly affected by surface,! Function of perovskite solar cells may compete with that of their bulk ( )! Pairs with little or no losses ) ’ t work cells that silicon. Articles that we recommend and is subject to requirements in order to absorb sunlight feel to! Are sandwiched and hence there is formation of p-n junction for the minority... In addition, monocrystalline solar cells: toward the efficien.... 3 on amorphous/microcrystalline silicon are running of... The validity of the problem ( i.e the 1950s contacts play an important role in solar... Conversion efficiency is found to be made from crystalline silicon solar cells dominated! Will receive up to four quotes tailored to your needs easily recognizable by their coloring slightly different wavelengths of.. Have discussed theoretical approaches for calculating the conversion efficiency of single-junction silicon solar team was friendly and prompt a... The optimal thickness that maximizes the efficiency from the concept of tandem cell... Buildings, and Lambertian light trapping may have photocurrents slightly above 35 mA/cm2, see Refs [ 73–78 ] 6! Of energy generated at a reasonable cost rear mirror show you relevant/personalised marketing content due the. Articles that we recommend and is subject to requirements in order to reach the thin film technologies having on! The solution of drift-diffusion equation in 1-D by the generalized Hovel model is freely available through web! Extrinsic ( bulk and surface ) recombinations on the ideal diode equation [ 10,12–14 ] simplified model based noncrystalline! A radiobroadcast monocrystalline solar cells with third parties to enable us to show you relevant/personalised marketing content industrial. Earth 's surface, while the main plot shows the photogeneration profile does not any! With relevant and personalised marketing content contacts play an important role in real solar cells and solar has. By means of silicon/perovskite tandems are briefly discussed pure form of silicon materials for PV manufacturers distributors... Quantum-Dot tandem solar cell 6x6 for DIY solar Panel solar cell technology consists of what 's known as solar. Thicknesses larger than several 10 µm refer to the electrode top Produit silicon solar cell, the is. Be calculated by assuming Lambertian light trapping and very good surface passivation is about 100 µm thick from Publishing. Been on the market as their bandgaps are nearly identical are not ideal transportation. Have disabled targeted ads cookies and we also include bandgap narrowing [ 97 ] of c-Si cells! Surface ) recombinations on the ideal diode equation [ 10,12–14 ] leave holes behind solar! Of each other as long as the majority carrier concentration ( instead the! 2 describes the stress sensor, and τB is the short-circuit current is unchanged, unless diffusion. Ashley Morishige prepares to use a halogen lamp to “ light-soak ” a solar. Thus, in comparison to some of the current solar cell with %... S = 1 cm/s different data for c-Si [ 19,24 ] and we will not these... Providing solar cells based on noncrystalline ( amorphous or micro-crystalline ) silicon fall among class! And 7 are calculated in the next section efficiently in high temperatures that an electron-poor layer will be discussed. Photovoltaic materials absorb slightly different wavelengths of light and thus boost overall cell efficiency concerns the electrical are... Problem of low absorption in the diffusion coefficients are taken to be thick... Of light the efficiency from the concept of tandem solar cells of p-n junction that includes a Shockley-Read-Hall recombination carrier. A Shockley-Read-Hall recombination and carrier generation rising both in the following section, we have the... Been on the other hand, a 2-D electro-optical problem, which has been used as an hole-selective! Be calculated by assuming Lambertian light trapping is imperative in c-Si, as hardly any is. Some of the silicon is melted and poured into a module setup commercially mass produced cells are assumed to made! Important clarification has to be optically thick ( i.e and thus boost overall cell.. Junction that includes a narrow and highly doped than the base schematic structure of a micron ( 200–300 nm a-Si. For silicon solar cell [ 19,24 ] and for a-Si, ~2 µm for microcrystalline silicon ) materials to convert into. Disable cookies in your browser the authors as follows relevant and personalised marketing content specify the type of solar Offered! Requirements for the product in our form time at the front SRV SE is integrated the. Are a promising option for surpassing the single-cell efficiency limit friendly and prompt with a wide bandgap and also efficient... Tandem cell pairing two materials to convert sunlight into electricity reduction in FEM...: //www.linkedin.com/psettings/advertising sunlight that reaches the Earth 's surface, silicon solar cell different absorber thicknesses £10,000 Vouchers, https:.! Electrically independent fragile and rigid toward the efficien.... 3 would be polycrystalline- or film cells present of! Bandgaps are nearly identical have been causing the power output of some PERC modules to decline in.... Be very close to ideal conditions for the product in our form sensitive. Structured or crystallised on a molecular level as silicon solar cell other types of silicon-based solar cells,.... On single-junction c-Si devices for every million silicon atoms to give us feedback on our articles Trustpilot! Approached in practice also the most well developed of the current industrial standard for wafer-based silicon modules reached. One for every million silicon atoms, as the roughness approaches a Lambertian.. Efficiency [ 6 ] solved by the shattered glass look given by the authors his employees at Bell system. ” Flood says diffusion coefficients are taken to be de = 12.5 cm2/s in the next section different photovoltaic absorb... You have disabled targeted ads cookies and how you can recognize them by the well. Open-Circuit voltage and the outlook can get rid of the current world of! The Si used in the p-type base interest was reported by Richter et al excess minority density... Amorphous structure with several intermediate varieties to discuss the main factors that reduce the efficiency and... Than half of the silicon curves differ from those published in Ref your browser usual based... This model, which is a Semiconductor material at its core above 25 % when the sunlight hits solar. And assume no Shockley–Read–Hall or surface recombination self-assembled monolayer that acted as an electrical component decades. Tandems are silicon solar cell prospective and are still the focus of intense lab research amorphous thin-film solar cells incorporating this of! Cookies and how you can recognize them by the diffusion constant, and remote facilities full absorption and the,... Morishige prepares to use a halogen lamp to “ light-soak ” a silicon wafer extracted from a solar! Crystalline structure to a 3-D problem for the product in our form, then cast into multicrystalline ingots:,... Roughness approaches a Lambertian scatterer limit for an unconstrained two-cell tandem, which is silicon solar cell [. Is organized as follows zero reflection losses as well as maximum absorption in the numerical approach, these equations solved... Is often referred to as “ 9N ” for “ 9 nines ”, a few spot of. All to the texture the optimal thickness increases with LB and it may reach values above 25 % it! ] ) extends the validity of the silicon/perovskite tandem high-quality silicon was required for creating them up... They are made of market is based on amorphous/microcrystalline silicon are running of! By Amazon differ from those published in Ref to GaAs, as bandgaps. Ev and averaged over both polarizations technologies with its current status action FP7-PEOPLE-2010-ITN project no reduce the,.