Using the same working principle as solarcells, thermophotovoltaic (TPV) cells can absorb the emitted photons from “blackbody” thermal sources to produce current flow and voltage bias, providing a direct and convenient energy conversion method from heat to electricity [1,2]. With the advantages of a fully solid state process, wide absorption spectra and direct DC power output, TPVs can find a variety of applications such as large and microscale power generators , solar thermophotovoltaics , remote or silent power and alternative power supply in space applications . Moreover, TPV systems can also be designed to absorb the thermal radiation from existing high temperature sources, which are prevalent in many industrial sites, serving as a waste heat recovery technique. For example in steel, glass and cement factories where temperatures can reach above 1000 K on the production line . The installation of efficient TPV systems in these places could generate additional electricity to power some of the on-site equipment, helping to reduce the overall energy consumption and carbon emissions. In the last few decades, different semiconductor materials such as silicon , InAs , InGaAs , GaSb [10,11] and GaInAsSb [12–15] have been investigated for TPV cell applications. Among these, the GaSb TPV cells with bandgap ~0.72 eV have achieved more than 0.5 V open circuit voltage (V oc )
Additional improvements are available through the addition of more than three junc- tions, though as the number of junctions approaches 10 the improvements become limited and cost ineffective . Several methods are under investigation to change the bandgap of the current-limiting middle junction. Compositionally graded metamorphic buffer layers of increasing In-content In x Ga 1−x As can be grown on top of the Ge bottom junction to change the substrate lattice constant towards that of material with a more favorable bandgap (1.1 to 1.2 eV) for the middle junction, to optimize both current-matching and spectrum-matching across sub-cells according to the detailed balance . This can create defects and dislocations due to the relaxation of strain which can propagate upwards and cause significantly decreased device performance in subsequently grown sub-cells (e.g.: the top junction) if not properly managed. To account for this, more advanced and complicated manufacturing methods such as inverted metamorphic (IMM) multi-junction solarcells, which rely on inverted growth and substrate removal, are used , . These methods begin with the growth of the top junc- tion, typically lattice-matched InGaP on a GaAs substrate, followed by a GaAs junction. A metamorphic InGaAs buffer layer is then grown and the lowest bandgap junction is grown, and any defects arising from the metamorphic layer no longer affect the top junctions. The active region is then removed from the substrate, which can then be polished and reused for future growths. A different approach makes use of the confined states in low bandgap nanos- tructures grown epitaxially within the middle junction material, as shown schematically in Figure 1.5, to engineer the bandgap to a more desirable effective bandgap E g(ef f ective) . E
Multijunction solarcells (MJSC) are instrumental in con- centrated (CPV) and space photovoltaic systems. The driving force for the material and technological develop- ment of MJSCs is the need for higher conversion effi- ciency. In CPV systems, the conversion efficiency is further increased owing to the use of concentrated light and therefore any efficiency gain that can be made by using more suitable materials and advanced design would lead to significant gain in overall system efficiency. The record CPV efficiency for lattice-matched GaInP/GaAs/ GaInNAsSb SC is 44% . On the other hand, the best lattice-matched GaInP/GaAs/Ge exhibit a peak efficiency of 43.3% under concentration  and 34.1% at 1 sun . Efficiencies as high as 50% have been predicted for cells with a larger number of junctions and high concentra- tion . To this end, a promising approach is to inte- grate dilute nitrides and standard GaInP/GaAs/Ge. Yet, so far, such heterostructures have exhibited low current generation .
enhancement can be achieved. Recently, Atre et al.  have modelled the effects of a spherical nanocresent consisting of a core of an upconverter material and a crescent-shaped Ag shell. A 10-fold increase in absorp- tion as well as a 100-fold increase in above-bandgap power emission toward the solar cell was calculated. A similar study has been performed using Au nanoparticles . Experimental proof has recently been reported by Saboktakin et al. . A related method is to enhance the absorption strength by nanofocusing of light in tapered metallic structures . At the edges, enhance- ment has been reported due to focusing of the light in these areas. The other option is enhancing the emission. In this case, the emission of the upconverter is enhanced by nearby plasmon resonances . Since the field enhancement decays away exponentially with the dis- tance to metallic nanoparticle, the upconverter species have to be close to the surface of the nanoparticle to benefit from the field enhancement effects. For organic molecules, this presents no problem because the molecules are small enough to be placed in the field. For lanthanide upconverters, this is more difficult because the ions are typically contained in materials with grain sizes in the micrometer range. However, several groups have managed to make nanosized NaYF4 particles [67,68]. This offers the possibility of plasmonic enhance- ment for lanthanide upconverters and decreases the light intensity required for efficient upconversion. Alterna- tively, upconversion using sensitized triplet-triplet annihilation in organic molecules at moderate mono- chromatic excitation intensities increases the a-Si:H cell efficiency as well [46,56].
Photovoltaics (PV) is a method of generating electrical power by converting solar radiation into direct current electricity using semiconductors that exhibit the photovoltaic effect. Photovoltaic power generation employs solar panels composed of a number of solarcells containing a photovoltaic material. Materials presently used for photovoltaics include monocrystalline silicon, polycrystalline silicon, amorphous silicon, cadmium telluride, and copper indium gallium selenide/sulfide. Due to the increased demand for renewable energy sources, the manufacturing of solarcells and photovoltaic arrays has advanced considerably in recent years.
(Ti/Pt/Au) layers. The fabrication processes of the devices were carried out in the following steps: (i) wet corrosion, (ii) n-type electrode evacuation, (iii) p-type electrode masking by photolithography, and (iv) p-type electrode deposition. The surface covering area of solarcells by electrodes accounts for 3.5% of the total surface area of the solar cell (the surface area of the solar cell defined of 0.25 cm 2 ). PbS
restrict them from reaching significantly higher efficiencies. In order to further reduce transmission and thermalization losses, additional junctions are required. Increasing the number of junctions has diminishing returns as shown in Figure 1.4 where the maximum detailed balance efficiency for solarcells with one to seven junctions is shown, both under one sun and 500x AM1.5G concentration . The figure shows that as the number of junctions is increased the percent increase in efficiency with respect to the number of junctions decreases. The current generated in a multiple junction device will equal the sub-cell with the lowest current due to Kirchoff’s current law. When each of the sub-cells is current matched to the other sub-cells no excess current from an individual sub-cell is lost to heat and higher efficiencies can be achieved. Current matching is an increasingly difficult condition to meet as the number of sub-cells increases because the available semiconductors with a common lattice constant is limited as shown in Figure 1.5. Much recent work has demonstrated triple-junction devices with differing lattice constants grown through metamorphic buffer layers [18, 19, 20]; however, the efficiency is limited by defects formed due to strain . As a result, much current work is focused towards the development of a next generation design, the IBSC [22, 23].
Of all the conventional energy sources present as of today, one of the cleanest yet efficient energies can be found from the sun. That is why humans have tried so hard to maximize the most abundant, yet least maximized form of energy in the whole planet – Solar Energy. Solar panels are already on circulation and can now be found virtually everywhere. The problem is that, not all can really avail, for the efficiency comes with a hefty price. Because of this, only those who have much investment can fully maximize this source of energy. There are many factors to consider in rendering a cost-and- energy-efficient mechanism. By experimenting with patterns found in nature, and integrating mathematics, possibilities in generating renewable source of energy are evident. Recent studies have been conducted in using Fibonacci and Golden Ratio concepts in constructing solar trees to produce more efficient solar panel arrays. The study of Ybo, Maisog and Bodabila (2017), which is one of the latest studies related to the concept, used Fibonacci sequence and golden ratio in the arrangement of the leaves in the trees, in arranging the solar panels. Their study showed that the solar panels arranged in this manner can generate approximately 7.77% more energy than the usual flat oriented array of solar panels. By trying to understand the relationships of all these elements, this research
Morphological characterizations were performed on both InAs NW samples grown with and without Au seeds on GaAs substrates. From SEM results, NW can grow with Au seeds on a (111)B GaAs substrate with a large base and narrow tip in the growth direction. Surface preparation greatly affects NWs density. NW growth direction mainly depends on the substrate. InAs NW uniformity is initially related to the Au seed coverage. A DI rinse after spin coating gold solution will help the gold see less congregated and better uniformity, and finally leads to a higher density of NWs. Increasing the V/III ratio from 6.5 to 38.8 results in better indium diffusion in the growth direction so a lower bottom diameter over length aspect ratio was as observed. III/V ratio affects the NW aspect ratio (length/bottom width), change from 12.00 to 38.93. However, higher V/III ratio will also cause lowest free energy directly change, then kinks was observed at V/III ratio at 38.8. Increasing temperature also shows a slight decrease in aspect ratio, but accelerates the growth rate in both axial and radial directions. On the other hand, NWs grown without Au seed using a pattern mask show no tapering along the growth direction with a smaller average diameter in 26 nm.
devices, which requires a high-temperature process, ranging from 400 to 1,050°C [14,15]. However, the high temperatures required for the CVD process degrade the characteristics of the solarcells. The ZnO nanotube with interest stemming from the facile synthesis with aligned and uniform ZnO nanotube arrays by using low- temperature (below 100°C) hydrothermal methods was also tried on the solarcells, without degrading the prop- erties of the solarcells . In this study, the growth of a ZnO nanotube on T-J solarcells via the hydrothermal growth method is investigated. The main motivation be- hind this study is the fact that nanostructures will act as a second ARC layer with an effective refractive index so that the refractive index of the total structure will per- form as a double-layer AR coating layer. The optical and electrical properties ofthe III-V solarcells with the above-proposed double-layer AR coating in this study are measured and compared.
great number of material combinations have been employed to fabricate IBSCs. Among them, self-assembled InAs quantum dot (QD) arrays fabricated by molecular beam epitaxy (MBE) have been widely studied as a building block to create the IB in the GaAs host material. However, the band gap combination and the location of IB in InAs/GaAs QD based IBSCs is not favourable and the upper limit efficiency is around 20% (1 sun) and 34% (1000 suns). 3–7 In order to improve the IBSC efficiency, host materials with much wider band gap such as AlGaAs or GaP are required. Recently, we have succeeded in the fabrication of GaAs QD arrays embedded in AlGaAs quantum-wire (QWR) host material by using a combination of neutral beam etching and atomic hydrogen-assisted MBE regrowth. 8 This top-down lithography and etching method is a strain-free approach, with the advantages of being able to precisely control the size, spacing, and arrangement of the QD during growth, which is difficult to achieve by self-assembling growth. In this study, we performed theoretical simulation of GaAs/AlGaAs QD arrays using a combined multi band k p and drift-diffusion transport method. The electronic structure, IB band dispersion, and optical transitions, including absorp- tion and spontaneous emission among the VB, IB, and CB, were calculated. Based on these pa- rameters, the theoretical conversion efficiency limit of GaAs/AlGaAs QD array based IBSC devices were calculated by a drift-diffusion model adapted to IBSC. 9–11
The development of the three-generation solarcells pro- duced a rich variety of solarcells, such as Si solarcells, III–V solarcells, perovskite solarcells (PSCs), thin film solarcells, dye-sensitized solarcells, and organic solarcells. However, practical, low-cost, and high-efficiency third-generation solarcells are yet to be demonstrated. Si solarcells are well developed and mature, but there is little room for further improvement [3–6]. III–V solarcells have a very high efficiency; however, its weakness is the high cost, which limits its applications [7–9]. Quan- tum dot solarcells have been receiving significant atten- tion because of their low cost and high efficiency, but most efficient devices have been prepared with toxic heavy metals of Cd or Pb [10–12]. Halide perovskites have recently emerged as promising materials for low- cost, high-efficiency solarcells. As the perovskite solar cell technology becomes more and more mature, the efficiency of perovskite-based solarcells has increased rapidly, from 3.8% in 2009 to 22.1% in 2016 [13–16]. However, the stability issues still require further studies.
15. C.Summonte, R.Rizzoli, D.Iencinella, E.Centurioni, A.Desalvo, F.Zignani - "Heterojunction solarcells on textured silicon" - Proc. of PV in Europe - From PV Technology to Energy Solutions, 7-11 October 2002, Rome, edited by WIP-Munich and ETA-Florence, (2002) 339-342.
While there is much promise in solarcells; delivery of an efficient and inexpensive PV panel in this lifetime may be asking too much. However it is important to re- member that solarcells are not the only way of produc- ing electricity from the sun. While solarcells use the sun’s light to create electricity, solar thermal systems use the sun’s heat to produce and is by far much more effi- cient. While no good in low light conditions, the heat created by the sun can be stored in a number of mediums from graphite to molten salt which means that within no time the ability to store this energy all night long will be upon us. Furthermore solar thermal is much cheaper than solar cell energy production and it is why the vast major- ity of solar power plants around the world use this form over any other .
There are many type power plant in India such as Thermal power plant, hydel power plant , nuclear power plant , solar power plant and wind power plant . In this paper, we are presented the renewable energy sources in order to meet an energetic demand in India with a lowest cost. These are beneficial the renewable energy sources like solar, wind, etc. This study focuses on making use renewable sources as an alternative source of energy. Renewable energy sources like solar, wind and renewable energy due to its availability, continuity and cleanness.
The development of society depends on access to electricity, for which the demand increases every year. From 2009 to 2017 human needs increased by 15%, reaching almost 19 TW/year [1, 2], and by 2050 it is expected to rise up to 27 TW/year (assuming linear growth). However, today we still depend mostly on fossil fuels, but reserves are limited and we need to develop alternative renewable energy sources. Solar energy has a great potential, since 1kW of energy falls on 1 m 2 surface perpendicular to the Sun’s rays on a clear day at sea level. If we were able to collect the sun´s energy falling on all available land (~ 150 Mkm 2 ) we could obtain 23,000 TW/year, which is much larger than expected human needs for 2050. Figure 1.1 compares the available energy from renewable (TW/year), fossil fuels (TW in total reserve) and the world energy needs in 2009 (16 TW). Clearly, solar energy shows the highest potential among the different renewable energies. Even when considering the limitations of land installation/transportation ( [4, 5]) and photovoltaic panels with an efficiency of 20%, the one-year solar potential would be of the order of the planetary reserves of coal. A multiple-year outlook unquestionably shows that if it could be successfully implemented, solar is the overwhelming energy solution for the future of the planet . Also, solar energy is the only energy source suitable for isolated and remote (off-grid) areas, as well as in urban areas and in space.
Adding an AR layer seems to be an effective way to improve the PCE of Si/PEDOT:PSS hybrid cells, with the mechanism of taking advantage of the difference in optical path between the top and bottom sides of the AR layer. As a result, the reflection was reduced and the transmis- sion was enhanced. Ultimately, higher intensity of the light reaching the absorber results in higher short-circuit current density (J sc ). However, limited by the quite lower
Optimization of the solar cell used in this work was based mainly on the band gap energies of the materials constituting the sub- cells and the temperature of the cell as the only design variables while setting the other parameters. An analytical model has been proposed for this purpose to determine the output parameters of the cell namely: the open circuit voltage (Voc), the short circuit current density (Jsc), the form factor (FF) and conversion efficiency (η). The influence of temperature on these parameters has been studied and reported in Table (4). We found that the coefficient of variation of the voltage as a function of temperature is - 2.4mV/° K for the top sub-cell, -2.2mV/° K for the middle sub-cell and -2.1mV/° K for the bottom sub-cell. The coefficient of variation of the voltage as a function of the temperature for the tri-junction cell is the sum of the coefficients of variation of the voltages of the three sub-cells composing the cell and is equal to -6.7mV/° K. Moreover, the decrease the open circuit voltage (Voc) contributes, in most cases, to the decrease of the efficiency (η) of the cell. This decrease is of the order of -0.027% /° K, - 0.024%/° K, -0.031%/° K and -0.072%/° K for the top, middle, bottom sub-cellssolar and the Tandem cell. As a perspective, we propose an improvement of the absoption of our cell by adding anti-reflective layers and a texturing of the front face to reduce the reflection, in addition to improving the efficiency of the tri-junction cell at high temperature by playing on technological parameters that can reduce the voltage coefficient as a function of temperature.
The prototype system CPV requires a tracking system in order to be axially aligned with the sun's rays . CPV systems in contrast to the traditional PV work only with the direct normal irradiance (DNI). In order to align the concentration optics it is necessary to use a solar tracking system, and in the specific case has been used a pointing system with bi-axial drivers motors for the tracker of the AKKUtrack ™. This device also allows you to measure the irradiance (W/m 2 ) of the sun and acquire it during the day . This is