The next generation solar cell materials have attracted tremendous research to improve their performance. In these materials, chalcogenides materials, inorganic perovskite and newly developed organometal halide perovskite have demonstrated their potential usage as solar cells owing to their exceptional properties to absorb the light and transform the light energy to current. Hence, understanding and improving these properties can promote further material design strategies for higher performance but lower the cost. Density functional theory is a widely used accurate calculation method to compute various physical properties of a material in an efficient way. In this thesis, we mainly use the density functional theory method to explore the light-matter interaction and its effect to the material's application as a solar cell. Alkali-metal chalcogenides have been found to exhibit appropriate band gaps for solar cells. We find that the volume compression can substantially enhance the optical dielectric function and the absorption coefficient intrinsically. The density function calculation and the tight-binding model show that this structure-property relation is mainly owing to the wavefunction phase change by compression, where the one-dimensional atomic chains play a significant role to relate the optical absorption and the structural change. But the high absorption does not guarantee high power conversion efficiency. This is because the excited carrier need to diffuse to the electrodes before they recombine. Organometal halide perovskites are found to have very large diffusion length and the long carrier lifetime. But the mechanism for such phenomena is still unknown. Here, by studying the structural change to the band structure and spin using CH3NH3PbI3 as an example, we find that the strong Rashba effect contributes to the long carrier lifetime by creating spin-forbidden electronic transitions, which slows down the radiative recombination and enhance the carrier lifetime. Furthermore, to study the spatial disorder effect to the electronic structure, we develop a large-scale tight-binding model which can highlight the structural disorder but still compute the band structure efficiency for very large systems. We find that the spatial disorder can create localized changes. These charge localization are spatially separated for valence band minimum and conduction band maximum. Therefore, their recombination will be further slowed down due to such spatial separation. In addition to these solar cell mechanism, we also studied the non-linear optical effect (bulk photovoltaic effect) in inorganic semiconductors. In this thesis, I use the example of
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coating, photocatalysts and so on [1-6]. Hesperidin shows a characteristic flavanone absorption spectrum with UV maxima at 286 and an inflection of low intensity at 330 nm. Hesperidin appear to be extremely safe and without side effects. Hesperidin has nontoxic both to the human beings and to nature, easily assimilated, non accumulative and caused no allergic reactions. Hesperidin is an abundant and inexpensive by-product of Citrus cultivation and is the major flavonoid in sweet orange and lemon. In paper work is focusing in the direction of systematic sample preparation, characterization, and find out optical parameters from physical phenomena such as absorption, transmission, reflection, and also application of solar cells in the form of DSSC for using Hesperidin pigment [8, 9].
shed light on ICT and energy transfer (ET) of the newly designed derivatives. We studied the effect of donor groups as it is expected that strong electron donor groups at one end and acceptor moiety at opposite side would tune the ICT through bridge, ultimately it would enhance the electron injection and electron coupling constant. It is anticipated that improved ICT would also improve the harvesting ability of sensitizers. The ICT process also plays a crucial role in achieving higher efficiency. This investigation aims helping to design efficient organic dyes in future that deliver qualitatively good descriptions of the electron injection of D-π-A sensitizers. The aim is also to design such derivatives which would be good materials as hetero-junction solar cells.
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absorbance value of 86% and ZnO with concentration of 0.1 M shows transmittance of 75% and an absorbance value of 80%. Then the different solar cell materials are patched with the thin-film wafer to find the most optically efficient solar cell material. The transmittance value has been found to be improved to 79% and lesser reflectance of 12%. The integrating sphere used offers uniform detection of reflectance even when the sample has different content. The future work can be carried out by further investigations with different silicon wafers and the future solar cell materials can be investigated such as indium tin oxide, cadmium coatings etc.
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Nickel oxide/graphene composite has been synthesized by chemical exfoliation method ; where the composite was examined by using Raman spectroscopy which showed D band at 1349 cm -1 and G band at 1587 cm -1 . The composite (NiO/graphene) clearly indicates a strong interaction between NiO and graphene sheets. Yin et al  used a monocrystalline ZnO nanorods (NRs) on RGO by electrochemical method; Raman study of RGO/ZnO NRs exhibited two identical peaks occur at 1350 and 1590 cm -1 , this could assign to D and G band of RGO. Similarly, Raman spectra has been used to characterize the solar cell materials in these reports [87-89]. Romanyuk et al  reviewed a specific group of non-vacuum method for the preparation of kesterite solar cell. Raman spectrum (fig.8) of selenized samples were measured at different depth materials conditions. For these depths of 0.3 mm, 0.4 mm and 1.2 mm, the corresponding reported kesterite phase (I st A 1 mode at 329 cm -1 , II nd A 1 mode
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inadequate film uniformity and intactness [8, 9]. Photo- voltaic thin-film solar cells or modules are usually made of an array of small cells which are interconnected in series and parallel to achieve the required voltage and current [1, 2]. The size of each cell should be kept small to achieve a higher device performance and efficiency, given that large-area thin films are more susceptible to manufacturing defects and imperfections compared to small-area films. Therefore, masks may be required to be used during the spray deposition and other casting processes to ensure that only specific areas are cov- ered, resulting in wastage of solar cell materials. To improve the uniformity of spray-on films, we have re- cently developed, implemented, and tested a modified coating technique, termed as substrate vibration-assisted spray-coating (SVASC), in which during the spraying process, controlled ultrasonic vibration is imposed on the substrate [10–12]. The imparted mechanical energy to the wet film leads to improvement in its uniformity as well its nano-structure and functionality. The imposed substrate vibration is also applicable to other casting methods, and has been used by others as well, such as for the fabrication of transistors  and nanowires . It has been shown theoretically [15, 16] and experimentally [11, 12] that the imposed substrate vibration can improve or deteriorate surface wetting, depending on the amplitude, power and frequency of the imposed vibration. In the following sec- tions, a manufacturing technique is proposed for the large
The charge transfer state (CT) potentially generated by the process of exciton dissociation is a Coulombically bound electron-hole pair, with the electron now in the lowest unoccupied molecular orbital of the acceptor molecule. In order for free charge carriers to be created, this CT state must also dissociate; the probability of this dissociation is given by Onsager-Braun theory. Lars Onsager first developed the theory of ion separation and recombination in weak electrolytic solutions 52,53 . His work described the probability of separation/recombination of an ion pair based upon the relative effect of an applied electric field; it is a solution to a steady state diffusion equation with infinitely long lived ions. While this work was experimentally verifiable for a variety of molecules 54–57 the theory broke down when applied to solid state mixed donor acceptor materials. Charles Braun introduced a modification to the theory to correct the problem; Onsager’s work predicted very large electron transfer distances that did not match those measured spectroscopically 58 . Braun’s modification mathematically incorporated the kinetics of CT
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The time line of photovoltaic solar cells starts with the discovery of the “photovoltaic effect” by Edmund Becquerel in 1839 while working with an electrolytic cell using two metal electrodes [2, 3]. Afterwards, Adams and Day observed PV effect in solid selenium in 1877 . In fact, following this work, Charles Fritts developed the first selenium solar cell using gold contact. This produced less than 1% conversion efficiency in 1883 . In 1887, James Moser discovered dye-sensitised solar cell using photoelectrochemical (PEC) cell. This continued until 1904 when the first semiconductor junction solar cell was produced by Wilhelm Hallwachs using copper and copper oxide . In 1905, Albert Einstein explained the photoelectric effect for which he later won Noble price. In 1918, the Czochralski method of silicon crystal growth was introduced. In 1932, PV effect was discovered in CdSe by Audobert and Stora. Following these developments, silicon solar cell with 4.5% efficiency was produced for space applications in the 1950s. Between 1959 and 1960, Hoffman Electronics produced 10-14% efficient commercial solar cells. The first high efficiency GaAs hetero-structure solar cell was produced in 1970. In 1977, the world's PV production exceeded 500 kW. The energy crisis of 1970s triggered extensive research and development activities in the PV area. In 1994, National Renewable Energy Laboratory (NREL) in United States produced concentrated solar cell exceeding 30% efficiency using GalnP/GaAs. In 1996, Michael Gratzel's group in Switzerland produced 11% dye-sensitised solar cell. In 2000s, organic solar cells came into the PV field and today hybrid solar cells combining organic and inorganic semiconductors are being researched extensively.
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MgZnO is a flexible Nano Crystal; with a low remix capability and tunable gap of 4.02 ev which can be a great alternative for CdS, if having high efficiency in solar cell. At this stage of the investigation of the buffer layer for GIGS, 0.2 um thick MgZnO Nano crystallineis intended. Figure(4), presents the new yield curve versus wavelength.
In 1954, D.M. Chapin, C.S. Fuller and G.L. Pearson, of Bell Laboratory, patented a way of making electricity directly from sunlight using silicon-based solar cells. The next year, the Hoffman Electronics- Semiconductor Division announced the first commercial photovoltaic product that was 2% efficient, priced at $25 per cell, at 14 mill watts each, or $1,785 per watt (in 1955 dollars). By the mid-1960s, efficiency levels were nearing 10 percent. As an outgrowth of the space exploration in the 1960s-70s, PV development increased dramatically. But worldwide hostilities and the threat of war turned the world more and more away from oil and toward renewable energy. The types of solar cell are shown in fig. (1).
The optical properties of thin films are very important for many applications, including interference devices, such as antireflection coatings, laser mirrors and monochromatic filters, as well as optoelectronics, integrated optics, solar power engineering, microelectronics and optical sensor technology depending on the reflectance and transmittance properties of the films during their preparation.
This paper demonstrates a novel method which will automatically track the sun’s position and accordingly change the direction of the solar panel to get the maximum output from the solar cell. As solar energy becomes increasingly popular in all parts of the world, all kinds of solar powered products are flooding the renewable energy market. One of them is the solar panel battery charger, the environment-friendly equivalent to a conventional battery charger. It converts light into a direct current, using solar cell modules i.e. a solar panel of varying volts for different uses
The world has experienced a huge increase in energy demand during the last 200 years. Fig. 1.1 gives the details about the significant rise of the global energy demand. It can be noticed that nowadays we consume over 10 times more energy than we did in 1820. Improved technologies and the fast growing population are mainly responsible for this huge increase. However, it is also clear that the majority of the energy resources that we rely on are not sustainable. Since crude oil is made over millions of years from an ancient biota, the overuse of oil means that we cannot depend solely on these resources for very much longer. Table 1.1 is based on the BP Statistical Review of World Energy 2010 that illustrates their estimate of the remaining energy resources over the world. According to this estimate, the most important energy resources—oil, could only last for 45 years, which means our current industry system will face a severe challenge by 2045. Besides the oil shortage, other energy resources (except solar power) can only support our economy for several decades; looking for alternative energy resources is imperative for all of us.
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Sel-sel solar yang diperbuat daripada tapak filem tipis CdTe mempunyai potensi kecekapan yang tinggi dan telah dikaji selama lebih 40 tahun kerana kelebihannya dalam teknologi pembuatan, pemendapan pantas, dan sifatnya yang sesuai sebagai pasangan kepada spektrum suria. Foto-voltan filem tipis Cadmium Telluride (CdTe) dikenalpasti sebagai bahan yang berpotensi tinggi kerana keunikan nilai jurangnya iaitu ~1.5 eV selain pekali penyerapan optiknya yang tinggi. Pada kebiasaannya, CdTe filem nipis sel solar adalah sejenis substrat yang dikonfigurasikan dengan lapisan tetingkap (CdS). Emas (Au) digunakan sebagai penyerap (CdTe) dan penghubung belakang. Proses pemendapan kedua-dua filem semikonduktor, CdTe dan Cd telah dilakukan menggunakan pemendapan vakum tinggi yang dibiarkan pada suhu bilik. Kepingan kaca yang mempunyai penghubung depan oleh fluorin yang didopkan timah oksida (FTO) digunakan sebagai substrat. Penghubung belakang dibuat untuk meningkatkan pengaliran cas-cas pembawa daripada lapisan CdTe ke elektrod. Struktur dan morfologi sel-sel dikaji dengan x- ray pembelauan (XRD), Sebaran Tenaga sinatan-x (EDX) dan keratan rentas Field Emission Scanning Electron Microscopy (FESEM). XRD filem tersebut menunjukkan proses polihabluran antara struktur kadmium sulfida dan kadmium Telluride dengan puncak masing-masing di 2 = 26.54 dan 23.71. Kajian XRD menunjukkan jarak antara zarah ialah (d) 3.34 untuk Cd dan 3.6 untuk CdTe. Imej keratan rentas FESEM menunjukkan dengan jelas lapisan-lapisan sel dan simpangan antara jenis-n dan jenis-p. Kecekapan sel-sel Cd dan CdTe dikaji dengan menggunakan tiga ketebalan yang berbeza. Menurut kajian yang dilakukan, sel-sel tersebut menunjukkan nilai kecekapan sekitar 7.98 %, dengan I CS = 19.1 mA dan V oc
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The current paper gives the prominent reviews of three important thin film solar technologies, namely Amorphous silicon (α-Si), Copper indium gallium selenide (CIGS) and Cadmium telluride (CdTe). Also discussed, the way these technologies are evolved based on their hold in the market and the reliability. The α-Si technology has almost been wiped out from the applications in terrestrial areas and hence the other two technologies are became a major share holder in the market. Thus, the CIGS and CdTe techniques are becoming healthy competitors for the primitive solar cells that are crystalline. However, the duration of the existence of a thin film solar technique is a major issuefor the exploration of the possibilities of building “An integrated PV cellsystem” that needs to be answered, prior spending the time and money.
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In the absense of catalyst, p-WSe 2 photoelectodes exhibited little to no activity toward the HER in aqueous solution either in the dark or under illumination, as shown in Figure 4.5. The crystals were also impressively stable toward oxidation, showing no significant anodic current until cycled to the oxygen evolution potential (∼1.25 V vs. RHE). We anticipated that the material might exhibit some HER catalytic activity, since MoS 2 and WS 2 materials were recently shown to be rather efficient HER electrocatalysts. 64,105,158,159 On the other hand, the HER activity of MoS 2 stems from exposed edge sites, rather than basal planes. Since our electrodes were highly crystalline and deliberately cleaved so as to expose a minimum of edge sites, the low observed catalytic activity is not at all incompatible with the possibility of similarly high catlytic activity for WSe 2 edge sites. In fact, the Cui group recently reported that MoSe 2 nanomaterials exhibit essentially identical high catalytic activity as MoS 2 , which implies that WSe 2 edges are likely also active toward the HER. 160
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reported however, the solar cells with CuO/ZnO structure have not widely fabricated and studied. Copper oxide (CuO) is metal oxide material that has been substantially explored for furious fields of applications. As a p-type semiconductor having narrow band gab of (1.35eV), CuO has great potential as a field emitter, catalyst and as a gas sensing medium. The physiochemical properties of CuO such as the photoconductivity and photochemistry can be tolerated for fabricating optical switches and solar. The Cu R 2 R o is of low cost, non toxic,
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For many agriculture needs, the alternative is solar energy. Modern, well-designed, simple-to-maintain solar systems can provide the energy wherever it is needed. Solar energy plays a vital role in drying agriculture products and for irrigation purpose for pumping the well water in remote villages without electricity. This technology on solar energy can be extended for spraying pesticides, fungicides and fertilizers etc., using solar sprayers.
Achieving a more competitive CSP technology requires progress in two paths. One is cost reduction in every step of the manufacturing, installation and operation of the plants. This path can produce a series of gradual small improvements that by themselves are not suﬃcient to reach suﬃcient competitiveness . The second path is development of higher performance solutions that will oﬀer much higher conversion eﬃciency, such as new thermodynamic cycles, new HTF materials, etc. However this path is long and diﬃcult, and requires not only a concept that works, but also an industrial development process that will demonstrate feasibility under ﬁeld conditions, reliability over decades of operation, and low cost of the proposed new concept.
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problems of CdTe solar cell development include the difficulty of doping p-type CdTe, the difficulty in obtaining low-resistance contacts to p-type CdTe, there combination losses associated with the junction interface , and cadmium toxicity related precautions that have to be considered during the manufacturing process. The main problem in developing CdTe for PV application is the instability of cell and module performance. The fundamental mechanisms that govern carrier transport and the effects of the diffusion length L, depletion width W, and primary heterojunction vs. back junction on the CdTe thickness t or back contact have not yet been well investigated and understood . Recently, Tang et al.  fabricated cadmium sulfide core/copper sulfide shell nano-wire solar cells using a low-temperature solution-based cation exchange reaction. The open-circuit voltage and fill factor, which determine the maximum energy that a solar cell can produce, promote the inexpensive and convenient manufacturing method of nano-wire solar cells. These new nano-wire solar cells also demonstrate 5.4% energy conversion efficiency, which is comparable to those of planar solar cells. The ability to produce efficient nanowire-based solar cells with a solution-based process and using earth-abundant elements  can significantly reduce fabrication costs compared with existing high-temperature bulk material approaches. A number of relatively simple, low-cost methods have been used to fabricate solar cells with efficiencies in the range 10- 16%. Some of the low-cost deposition methods that show promise include:
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