Papers by Keyword: Solar Cell

Abstract: Silicon nanowires (SiNWs) based solar cells are passivated by native oxide and SiN_x bi-layer. In comparison with cells passivated by SiN_x single layer, bi-layer passivation exhibits higher effective minority lifetime, illustrating a better surface passivation effect, which leads to a gain of internal quantum efficiency in the short wavelength range, a better output performance with an increase of 0.16% in efficiency. The data obtained from this work is fundamental and has some reference value for future studies.

Abstract: Short circuit current density (J_sc) and photoelectric conversion efficiency (η) of the different material quantum dot intermediate band solar cells (QD-IBSCs) under full concentrated sunlight were compared in this work. The QD-IBSCs were designed with QDs formed from different excitonic Bohr radius semiconductors embedding in the different wide band gap materials. Modulation doping was used to realize partially filling the IB with electrons in QD, the influence of localized states from doping on IB was also considered. The performance of these SCs was numerically simulated based on the detailed balance principle. The J_sc and η in QD-IBSCs can be adjusted via tuning the position and density of states of IB due to varying the mean size (d) and doping level of QDs in absorption region. Under the same doping level in an identical host gap material with ΔE_G=2.0 eV, the J_sc and η of the Si QD-IBSCs can be optimized with 4.3 nm-QDs, however, those of CdTe devices raises while those of Ge cells drops with increasing the sizes of QD from 2 nm to 8 nm. With changing the host gap ΔE_G, variation of the IB energy level E_H with respect to valence band corresponding to the maximum η_m was explored, dependence of η on the operation voltage was analyzed, and the impurity effect on the η was taken into account. Present work indicates that an appropriate band gap material should be adopted to fabricate QDs to embed in suitable doped host gap one to obtain the high performance QD-IBSC.

Abstract: Cast mc-Si ingots are widely used in photovoltaic manufacturing. The utilization rate of industrial polycrystalline silicon ingot only about 70%, most of them are less than 70%, the main influence factors are casting process, raw and auxiliary materials as well as the crucible material. The growth process and the overall characteristics of 420 kg polycrystalline silicon ingot are analyzed and researched in detail. This paper focuses on the distribution characteristics and causes of the casting defect which are analyzed in detail and discussed, at the same time suggestions are given to improve the utilization rate of the ingot.

Abstract: This paper reports mainly a work of the influence of annealing on the solar cell which the active layer is made from poly (3-hexylthiophene) and [6,-phenyl C61 butyric acid methyl ester. XRD analysis of the active layer indicates that the layer annealing can improve the film crystallization. With the reducing of light reflection rate, the light transmittance rate improves due to the annealing treatment of the active layer. Comparing in various annealing temperature, it is found that a better result can be obtained when the annealing temperature is 140 °C. At this annealing temperature, the organic solar cell brings out relatively high conversion efficiency in the experiment.

Abstract: A new TiO₂-nanoSiO₂ hybrid film is prepared through adding the nanosized SiO₂ into the TiO₂. A more environmental and simpler method is found to prepare CdSe quantum dots (QDs) sensitized TiO₂nanoSiO₂ hybrid films for the quantum dots-sensitized solar cells (QDSSCs) application. The prepared colloidal CdSe QDs (~2.6nm) was linked to the TiO₂-nanoSiO₂ hybrid film using 3-mercaptopropionic acid (3-MPA) as a linker molecule slowly with drop and drop. The power conversion efficiency of 1.33% was achieved using the sensitization photo-electrode prepared by using TiO₂nanoSiO₂ hybrid film modified with CdSe (TiO₂-nanoSiO₂/CdSe) under the illumination of one sun.

Abstract: To improve the electrical performance and reduce the fabrication cost of the solar cell, thin-film solar-cell concepts are widely explored. In this context, many studies have been carried out to study the impact of the thin thickness of the material on the solar cell behavior. Recently, the Si_1-xGe_x/Si heterostructure is considered as attractive alternative for photovoltaic applications due to their band structures, which allow getting an additional gain in the device efficiency. However, the growth of this material is not totally controlled, and the presence of interfacial defects is more than estimated after a growth run of this material. Therefore, new experimental and numerical investigations which capture the Si1-xGex/Si heterostructure behavior should be developed in order to build a complete Si_1-xGe_x/Si-based solar cell model for photovoltaic applications. In this paper, we aim at highlighting the immunity of the Si_1-xGe_x/Si heterostructure against the defects degradation effect at nanoscale level (thin films). The effect of interface defect on the heterostructure has been carried out by extensive simulation using Atlas 3-D simulator, including the device dimension and the Ge Mole fraction effects.

Abstract: Transition metal chalcogenide molybdenum ditelluride (MoTe₂) thin films have been electrosynthesized cathodically on indium tin oxide-coated (ITO) conducting glass substrates from ammonaical solution of H₂MoO₄ and TeO₂. The electrode potential was varied while the bath temperature was maintained at 40±1 oC and deposition time of 30 minutes. Highly textured MoTe₂ films with polycrystalline nature are observed by X-ray diffraction analysis. Compositional analysis by EDX gives their stoichiometric relationships. Scanning electron microscope (SEM) was used to study surface morphology and shows that the films are smooth, uniform and useful for device fabrication. The optical absorption spectra showed that the material has an indirect band-gap value of 1.91-2.04 eV with different electrode potential. Besides, the film exhibited p-type semiconductor behavior. Keywords: Molybdenum ditelluride; Thin films; Electrodepositon; Solar cell;

Abstract: Bulk heterojunction solar cell has received significant attention over the past decade due to low cost power generation and the potential to develop a clean renewable energy source [. We investigated the effect of different type of metal cathodes on the power conversion efficiency of bulk heterojunction solar cell based on a blend of conjugated polymer poly [2-methoxy 5-(2-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) with titanium dioxide (TiO₂). In this case of study, Aluminum (Al) and gold (Au) has been chosen as the metal cathode due to the difference of work function and their wide application in hybrid solar cell. We show that the choice of metal cathode plays a role in determining overall device efficiency through their impact on short-circuit current, open circuit voltage and fill factor due to the influence of work function. It is found that the device employing Al metal cathode which has low work function is showing a comparable performance to the Au metal electrode with fill factor of over 20 % and a power conversion efficiency of 3.3x10^-3 %. Overall it is demonstrated that the matching between the work function of the cathode and photoactive layer MEH-PPV: TiO₂ is the most important factor towards best bulk heterojunction solar cell performance.

Abstract: Solar cells of common sizes contains many of these defects and it is not easy to determine the influence of particular defects on the characteristics of the whole solar cell. Therefore, in our research we use samples of size of square centimeter at which we can disentangle the influence of the defect. We localize the defect by using a CCD camera, we measure the electrical, thermal and optical properties of the sample and then study it by means an electron microscope, we find the damaged structure and put it to focused ion beam. We expect the change in electrical, thermal and optical properties of the sample.

Abstract: Presented research is involved in excess electrical currents created when the silicon material contains cracks and fractures. We performed transport characteristics measurements and electrical noise measurement as well as sample visible and deep infra-red imaging. It turns out that mechanical induced defects are followed by specific electric characteristics. We observe crack-related local breakdowns and local overheating. It is also followed by the electrical current fluctuation in the 1/f form. All regions are thermally but also electrically stressed and the irreversible sample degradation originates. It could be pointed out that our detection methods are very sensitive and they could be also used for analyses of different materials.