ciale silicon solar cell and under monochromatic illumination modulation frequency and irradiation. This study allowed us to remember the expressions of the global generation rate depending on the type of illumination and expressions of the diffusion coefficient according to some electrical parameters. In addition, the study of the in- trinsic recombination velocity at the junction has allowed us to highlight the different relationships of the intrin- sic recombination velocity at the junction following the plans and the type of illumination. Indeed, this study
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 N. Honma and C. Munakata, «Sample thickness dependence of minority carrier lifetimes measured using an ac photovoltaic method», Japan. J. Appl. Phys. 26,(1987) 2033-6.  A. Dieng, I. Zerbo, M. Wade, A. S. Maiga et G. Sisoko, «Three-dimensional study of a polycrystalline silicon solar cell: the influence of the applied magnetic field on the elctrical parameters», Semicond. Sci. Technol. 26, (2011) pp: 5023- 5032.
The aim of this study is to show the influence of the wavelength on the electrical parameters of vertical parallel junction silicon solar cell by use of impedance spectroscopy technique. The Bode diagrams of the diffusion capacitance are shown for different wavelengths while the solar cell op- erates under both open circuit and short circuit conditions. The Nyquist diagram of the diffusion capacitance has shown the extension of the space charge region for various wavelengths.
Given the low conversion efficiency of solar cells (M. A. Green, 1995), many researchers have been conducted to increase this conversion efficiency by improving existing structures by passivating quasi-neutral regions (T. Dullweber et al., 2011; T. Dullweber et al., 2012), adding a back surface field (L. M. Koschier et al., 1998; Kaminski et al., 2002) or by creating novel structures like vertical junction (Terheiden et al., 2000; R. Sarfaty et al 2011), triple junction (Meusel et al., 2007) and bifacial (G. Untila et al, 2008; C. Duran et al., 2010) solar cells. In this work we will show the effects of illumination wavelength, grain size, grain boundary recombination velocity and junction recombination velocity on the dynamic impedance of a vertical parallel junction solar cell.
The efficiency of a solar cell is directly linked to the density of carriers in the base of the solar cell which is a function of the support material band gap of this solar cell, the illumination mode, the carriers diffusion parameters and recom- bination parameters. Several analytical and experimental studies have been done in monochromatic   and multispectral      illuminations. Some studies have also been done on light illumination effects on monofacial    , bifacial      and amorphous  solar cells. It appears through these studies that the increase of illumination power comes with an in- crease of the density of carriers in the base of the solar cell  . Some studies put also in evidence that external parameters such as magnetic field   electric field  , light concentration   can influence the diffusion coefficient of a silicon solar cell.
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and the conversion efficiency increases from 24.5% to 25.2%. In experimental study, E. Serafettin  finds in red color wavelength of a monochromatic illu- mination that the open circuit voltage decreases with the increase of the electric field but the short circuit current does not change. However, we observe an in- crease of 0.7% about conversion efficiency. This efficiency is better improved compared at efficiency of the silicon polycrystalline solar cell which does not in- fluence by the electric field . This increase can improve with the reduction of distance between the both aluminum conductors. It can also improve by the in- crease of the number of the solar cells used for the creation of the electrical field and choosing the good angle between internal and external electric fields. Moreover, the short distances values bring the operating point of the solar cell in vicinity of the open circuit state.
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etching process is facilitated by silver nanoparticles which act as catalytic sites. The etching times for the fabrication of nano-pores on the surface are established. The optical properties of the nano-structures on the surface of silicon solar cell were investigated by spectrometer measurements. The samples presented a total reflection coefficient lower than that of silicon solar cells without the treatment. The global efficiency of the silicon solar cell depends on the chosen preparation conditions for the silver ion concentration, and time of wet etching. The textured surface of solar cells showed an increase in efficiency, with a circuit photocurrent higher than that of a reference silicon solar cell without texturing. The J-V curves of various silicon cells are presented and discussed in correlation with the surface morphology.
results in power shortage, so solar PV system is proven best in atmospheric conditions of region like India. Efficiency and Fill factor of solar PV system are degraded due to dust and similar pollutants. The accumulation of dust on the surface of a photovoltaic module decreases the radiation reaching the solar cell and produces losses in the generated power. Dust not only reduces the radiation on the solar cell, but also changes the dependence on the angle of incidence of such radiation. This work presents losses caused by the accumulation of dust on the surface of photovoltaic modules and effect of dust layers on the transmissivity of PV module glass.
temperature zones of RTA process have been achieved properly which can significantly enhance the efficiency of solar cell. Moreover, doping concentrations have to be further optimized and carefully characterized to get more improvement. The efficiency of the fabricated solar cell was 3.3%. As we have huge sunlight, we can convert this sunlight to electricity with the help of a solar cell as we have developed. In the near future, optimizing all the challenges the laboratory in Bangladesh Atomic Energy Commission (BAEC) will play a pioneer role in developing as well as promoting solar cell fabrication technology in the country.
An alternative approach is pictured in Figure 1.1b. This n-i-p structure is utilized in low mobility materials such as hydrogenated amorphous Si (a-Si:H) and microcrystalline Si (µc-Si). Carriers in such materials cannot diffuse far enough to be collected via a traditional p/n junction. Instead, the absorber layer is much thinner (hundreds of nm as opposed to the typical thickness of hundreds of µm in a c-Si based device) and is intrinsic so that the built-in electrostatic field induced between the heavily doped p and n regions extends throughout the device. Thus photo- excited carriers are collected via electrostatic drift in these structures. The devices considered in Chapter 4 are based on a n-i-p approach. Since holes are typically less mobile than electrons, these cells are almost always fabricated such that illumination occurs through the p-layer. Because more carriers tend to be generated near the front of a device due to exponential Beer-Lambert absorption, this design rule ensures the average collection length for holes is shorter than for the more mobile electrons. Convention dictates that the layers are named in the order they are deposited. Thus an n-i-p cell pictured in Figure 1.1b would be a substrate device and a p-i-n cell would be a superstrate device; in either case illumination occurs through the p-layer. Another feature of the n-i-p approach is that a transparent conductor is often used to make top contact because the lateral conductance of the heavily doped p-layer is much less than in a crystalline emitter, thus a metallic grid front contact alone is not feasible due to increased series resistance in the emitter and the associated power loss.
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Solar cells use semiconductors to capture light. Each photon of light that is absorbed raises an electron in the semiconductor material to a high-energy state. The electron then drifts away from the net positive charge left behind (termed a ‗hole‘) and this generates a current, which is drawn off as electricity. Silicon makes excellent solar cells – it‘s the right colour, absorbing across the visible and near infrared parts of the solar spectrum, and makes reasonably efficient cells. However, its efficiency has limitations: for silicon to absorb enough light, relatively thick slabs (typically 0.2 mm) need to be used. Semiconductor-grade silicon is an expensive material, too expensive to make the scale-up of silicon-based solar panels a feasible prospect. After the world-wide photovoltaic market more than doubled in 2010, the market grew again by almost 30% in 2011, despite difficult economic conditions. In 2011, the photovoltaic industry production reached a world-wide production volume of around 35 GW and another moderate increase is expected for years to come. Yearly growth rates over the last decade were on average more than 40%, which makes the photovoltaic industry one of the fastest growing industries at present [5 – 7].
The photovoltaic properties of a-Si:H solar cell was measured by solar simulator under air mass 1.5 G con- dition. Figure 4a shows the photocurrent density-voltage behavior. The planar pin a-Si:H solar cell exhibit short- circuit current density [Jsc] of 5.0 mA/cm 2 and power conversion efficiency [PCE] of 1.43%. The detailed photovoltaic properties were listed in Table 1. With sur- face nanocone structure, the Jsc increases to 5.7 mA/ cm 2 which is 14% enhanced. Additionally, the PCE also increases to 1.77% which is 24% enhanced. The short transport path for the electron in the a-Si:H nanocone contributes the additional 0.7 mA/cm 2 photocurrent . However, the native oxide and defects on the a-Si:H nanocone after RIE etching may either restrict part of photocurrent transport or act as recombination centers that increase the series resistance as high as 160 Ω·cm 2 . The H 2 plasma was used to remove the native oxide
Silicon nanowires (SiNWs) have received considerable attention as base materials for third-generation photovoltaic (PV) devices because they lend themselves to large- scale production with enhanced light trapping and increased overall performance. Previous studies have grown SiNWs on indium tin oxide-coated glass substrates by the pulsed plasma-enhanced chemical vapour deposition method (PPECVD) using tin (Sn), aluminum (Al), gold (Au) and zinc (Zn) as catalysts.
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at temperatures below 250°C was a merit that leads to a decrease in the thermal budget of solar cell production processes. In this respect, a-Si:H is expected to be a good passivation choice for Si nanostructure solar cells. Crozier et al.  demonstrated that in situ amorphous Si/SiNW surface recombination decayed just about 2 orders of magnitude compared with SiNWs alone. The surface passivation capability of amorphous silicon was proved by the increase of lifetime and carrier diffusion length. However, this passivation effect was not investi- gated on the SiNW solar cell performance. In a previous study , SiNWs were synthesized using the VLS process which was a bottom-up synthesis approach. Indeed, those SiNWs differ from SiNWs synthesized by metal-assisted wet chemical etching (top-down ap- proach), especially in the defect type and quantity, SiNW density, as well as doping mechanism .
Solar energy will be even more relevant for developing nations whose energy requirements are increasing rapidly as a result of large scale industrialization and growing population, for these nations, it is easier to switch directly to renewable energy sources, since they are yet to choose their options. The energy crisis of the seventies has encouraged research in energy related areas, especially those, useful for utilization of solar energy.
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Solar trackers can be active or passive and may be single axis or dual axis. Single axis trackers normally use a polar mount for maximum solar efficiency and employ manual elevation (axis tilt) adjustment on a second axis, which can be adjusted regularly during the year. Trackers can be relatively inexpensive for photovoltaics. This makes them especially effective for photovoltaic systems using high-efficiency panels. Solar trackers usually need inspection and lubrication on a regular basis. Active trackers, which use motors and gear trains, are controlled by an electronic circuit responding to the solar direction.
Figures (1- a, b, c, d & e) show the photograph and the scanning probe image processor analysis of gold nanoparticles on the top surface of the silicon solar cell before annealing: figure (a) shows a photograph taken with optical microscope. Figure (b) shows a magnified picture of the same sample, and figure (c) is a panel presents height profiles measured along the sample surface. (d) represents the three dimensional view, and (e) presents its roughness results histogram. The results show the followings: roughness average (sa) =54.7808nm, peak- peak (Sy) =512.831nm, max valley depth (Sv )=225.272 nm, max peak height (Sp)= 287.558nm, mean height (Smean) =-1.9 nm E-006 nm. In figure (f)represents the surface particles distribution.
De Boer et al. (2010) noticed an increase in PL intensity for Si nanocrystals and shifts to longer wavelengths for small-sized nanocrystals. Our results are in agreement with other studies that synthesized SiNWs using Au as a catalyst and obtained red emission peaks (Colli et al. 2006; Wu et al. 1996). Moreover, the blue PL could have come from the Si-rich oxides including very small molecular-like Si clusters in the silicon oxides shells which supports the hypothesis that violet/blue PL originates from the SiOx amorphous matrix covering the c-SiNW core (Zhao et al 2013). On the other hand, the shape and intensity of the PL spectra confirm that the emission bands cannot correspond to the SiNWs core where the intensity of the c-Si should be high (Ma et al. 2008).
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The fabrication of solar cell grade silicon (SOG-Si) feedstock involves processes that require direct contact between solid and liquid phases at near equilibrium conditions. Knowledge of the phase diagram and thermochemical properties of the Si-based system is therefore important for providing boundary conditions in the analysis of processes. A self-consistent thermodynamic description of the Si-Ag-Al-As-Au-B-Bi-C-Ca- Co-Cr-Cu-Fe-Ga-Ge-In-Li-Mg-Mn-Mo-N-Na-Ni-O-P-Pb-S-Sb-Sn-Te-Ti-V-W-Zn-Zr system has recently been developed by SINTEF Materials and Chemistry. The assessed database has been designed for use within the composition space associated with SoG-Si materials. The thermochemical database has further been extended to calculate the surface tensions of liquid Si-based melts. In addition to thermochemical and phase equilibrium calculation, several surface-related properties (temperature and composition gradients, surface excess quantity etc.) are able to simulate simultaneously using the database. The databases can be regarded as the state-of-art equilibrium relations in the Si-based multicomponent system. [doi:10.2320/matertrans.M2009110]
 Ngom, M.I., Zouma, B., Zoungrana, M., Thiame, M., Bako, Z.N., Camara, A.G. and Sissoko, G. (2012) Theoretical Study of a Parallel Vertical Multi-Junction Silicon Cell under Multispectral Illumination: Influence of External Magnetic Field on the Electrical Parameters. International Journal of Advanced Technology & Engineer- ing Research , 2, 101-109.
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