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Xinyu Liu - One of the best experts on this subject based on the ideXlab platform.
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the influence of surface structure on diffusion and passivation in Multicrystalline silicon solar cells textured by metal assisted chemical etching mace method
Solar Energy Materials and Solar Cells, 2018Co-Authors: Xiaowa Dai, Rui Jia, Ke Tao, Chao Zhang, Pengfei Zhang, Xinyu LiuAbstract:Abstract It is important to improve the efficiency of solar cells textured by the MACE method, and the surface morphology has a significant effect on the efficiency. In this paper, we textured Multicrystalline Wafer using MACE method, and the surface morphology was further modified by post-etching process to achieve high efficiency. The influence of structure on diffusion and surface passivation was studied. It reveals that surface structure has a big effect on diffusion and passivation, thus affecting the efficiency. Structure with large aspect ratio results in heavily doped regions and poor passivation performance. Finally, large area solar cells with the efficiency of 19.08% and 19.11% were obtained on slurry wire and diamond wire saw Multicrystalline Wafer respectively, which is 0.5% and 0.8% absolutely higher than the cells with traditional acid texturing.
W C Sinke - One of the best experts on this subject based on the ideXlab platform.
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alkaline etching for reflectance reduction in Multicrystalline silicon solar cells
Journal of The Electrochemical Society, 2004Co-Authors: J D Hylton, A R Burgers, W C SinkeAbstract:The reflection reducing properties of alkaline-etched Multicrystalline Wafers are investigated experimentally for high concentration saw-damage etching and low concentration texture etching. Saw-damage etch textures are too flat for multiple bounce reflectance in air, with only 1.6% of the Multicrystalline Wafer surface calculated to have facet tilt angles above 45° whereby double-bounce reflectance is guaranteed. Texture etching yields 3% lower reflectance in air, due to high angled ~up to 54.7°! pyramidal structures on near ~100! orientations, whereby 13% of the Multicrystalline etch surface has tilt angles above 45°. However, under encapsulation, light is coupled more effectively into the silicon; reflectances for the saw-damage and texture-etched Wafers compare only 7 and 5.5% higher, respectively, than upright pyramid textures on monocrystalline silicon~100!, compared to 18 and 15% higher in air. This is because a far larger proportion of the Multicrystalline Wafer ~around 40% for the two etches! has tilt angles above 20.9° whereby escaping light is totally internally reflected at the glass-air interface. For texture etching, not only $111% planes are stable to etching but the whole range of $XXY% crystallographic planes between these and $110% orientations, contrary to the accepted texture etching theory. © 2004 The Electrochemical Society. @DOI: 10.1149/1.1738137# All rights reserved. Alkaline etchants for solar cell processing .—As a standard practice alkaline etchants are employed in solar cell processing. High temperatures ~above 100°C! and concentrations ~around 10 M or more! of alkali are used for the removal of sawing damage for as-cut silicon Wafers. These etching conditions are chosen in order to remove the required depth of saw-damaged silicon as quickly as possible. In contrast, low temperatures ~below 100°C! and concentrations ~,0.5 M! of alkali are used in the processing of ~100!-oriented monocrystalline Wafers. In this case, the anisotropic action of the alkaline etchant is exploited, whereby slow etching planes, apparently of $111% orientation, are exposed and intersect to form upright four-sided pyramids with square bases up to 10 3 10 mm 2 . These pyramidal textures have geometries which allow sunlight to be more easily coupled into the silicon, and thus to allow as much light as possible to be absorbed and converted to electrical current in the solar cell. Reflectance reduction through geometrical texturization .—Figure
J D Hylton - One of the best experts on this subject based on the ideXlab platform.
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Light coupling and light trapping in alkaline etched Multicrystalline silicon Wafers for solar cells
2006Co-Authors: J D HyltonAbstract:The reflection reducing and light trapping properties of alkaline etched Multicrystalline silicon Wafers are investigated experimentally. Following an overview of various chemical texturisation methods and their effect upon the surface morphology, a high concentration saw-damage etch and a low concentration texture etch are assessed. Etch surface geometries are quantified in terms of the tilt and azimuth angles of the texture features on a per orientation basis. In the case of saw-damage etching, the {100}, {111}, {110}, {311} & {211} sets of crystallographic planes are stable to the etch. The resulting textures are too flat for multiple bounce incidence in air, with only 1.6% of the Multicrystalline Wafer surface calculated to have facet tilt angles above 45° whereby double bounce incidence is guaranteed. For texture etching, it is found that contrary to the accepted principles of texture etching, not only {111} planes are stable to etching but the whole range of {XXY} crystallographic planes between these and {110} orientations, challenging the validity of the accepted theory. The orientations in the vicinity of the (100) yield (tilted) pyramid structures with etch facets angled up to 54.7°, whereby 13% of the Multicrystalline etch surface has tilt angles above 45°, and reflectances are 3% lower than for saw-damage etched Wafers in air. However, under encapsulation, both saw-damage and texture etched Multicrystalline Wafers couple light more effectively into the silicon. Encapsulated reflectances compare only 7 and 5.5% higher respectively than upright pyramid textures on monocrystalline (100) silicon, compared to 18 and 15% higher in air. This is because a far larger proportion of the Multicrystalline Wafer is facetted at tilt angles greater than the 20.9° satisfying the condition for total internal reflection of escaping light at the glass-air interface. Light trapping is also found to be dependent upon the facet angles of the geometrical surface texture. Considering the principal triangle of (100):(110):(111) orientations, for saw-damage etching, central orientations around the (321) with the highest facet tilt angles, provide high levels of light trapping which with a back surface reflector can approach Lambertian levels. In contrast, the flat surfaces yielded on saw-damage etched (100) and (111) orientations have poor light trapping properties. For texture etching, light trapping is greatest for the highly facetted pyramidal textures on near (100) orientations, decreasing to the levels of polished silicon for the flat etching {XXY} orientations. The particularly poor light trapping for the {XXY} texture etched orientations means that overall, saw-damage etched Multicrystalline Wafers have higher levels of light trapping (in terms of the absorption efficiency of light after its initial coupling into the silicon) than texture etched Multicrystalline Wafers etched to the same depth. However, front surface reflection, particularly under encapsulation, has a far greater influence upon the electrical output achievable than light trapping for the 200 µm thick Multicrystalline Wafers investigated. Thus texture etched Multicrystalline Wafers, with lower reflectance by virtue of the particularly high facet angles (up to 55°) present upon (tilted) pyramid textures, have slightly higher maximum short circuit current values than saw-damage etched Wafers.
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alkaline etching for reflectance reduction in Multicrystalline silicon solar cells
Journal of The Electrochemical Society, 2004Co-Authors: J D Hylton, A R Burgers, W C SinkeAbstract:The reflection reducing properties of alkaline-etched Multicrystalline Wafers are investigated experimentally for high concentration saw-damage etching and low concentration texture etching. Saw-damage etch textures are too flat for multiple bounce reflectance in air, with only 1.6% of the Multicrystalline Wafer surface calculated to have facet tilt angles above 45° whereby double-bounce reflectance is guaranteed. Texture etching yields 3% lower reflectance in air, due to high angled ~up to 54.7°! pyramidal structures on near ~100! orientations, whereby 13% of the Multicrystalline etch surface has tilt angles above 45°. However, under encapsulation, light is coupled more effectively into the silicon; reflectances for the saw-damage and texture-etched Wafers compare only 7 and 5.5% higher, respectively, than upright pyramid textures on monocrystalline silicon~100!, compared to 18 and 15% higher in air. This is because a far larger proportion of the Multicrystalline Wafer ~around 40% for the two etches! has tilt angles above 20.9° whereby escaping light is totally internally reflected at the glass-air interface. For texture etching, not only $111% planes are stable to etching but the whole range of $XXY% crystallographic planes between these and $110% orientations, contrary to the accepted texture etching theory. © 2004 The Electrochemical Society. @DOI: 10.1149/1.1738137# All rights reserved. Alkaline etchants for solar cell processing .—As a standard practice alkaline etchants are employed in solar cell processing. High temperatures ~above 100°C! and concentrations ~around 10 M or more! of alkali are used for the removal of sawing damage for as-cut silicon Wafers. These etching conditions are chosen in order to remove the required depth of saw-damaged silicon as quickly as possible. In contrast, low temperatures ~below 100°C! and concentrations ~,0.5 M! of alkali are used in the processing of ~100!-oriented monocrystalline Wafers. In this case, the anisotropic action of the alkaline etchant is exploited, whereby slow etching planes, apparently of $111% orientation, are exposed and intersect to form upright four-sided pyramids with square bases up to 10 3 10 mm 2 . These pyramidal textures have geometries which allow sunlight to be more easily coupled into the silicon, and thus to allow as much light as possible to be absorbed and converted to electrical current in the solar cell. Reflectance reduction through geometrical texturization .—Figure
Martin A. Green - One of the best experts on this subject based on the ideXlab platform.
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Crystalline and thin-film silicon solar cells: state of the art and future potential
Solar Energy, 2003Co-Authors: Martin A. GreenAbstract:Abstract Bulk crystalline silicon solar cells have been the workhorse of the photovoltaic industry over the past decades. Recent major investments in new manufacturing facilities for monocrystalline and Multicrystalline Wafer-based cells, as well as for closely related silicon ribbon and sheet approaches, ensure this role will continue well into the future. Such investments suggest that the silicon Wafer-based approach has successfully withstood the challenge mounted by thin-film chalcogenide-based cells, in the form of polycrystalline films of CdTe and CuInSe 2 , as well as that mounted by thin-film cells based on amorphous silicon and its alloys with germanium. The encumbent now faces a fresh challenge by a new wave of thin-film technologies developed in the 1990s, more closely related to the bulk approach and with some advantages over the earlier contenders. One new approach is based on a stack of two silicon thin-film cells, one cell using amorphous silicon and the other mixed-phase microcrystalline silicon. The second uses silicon thin-films in polycrystalline form deposited onto glass, even more directly capturing the strengths of the Wafer-based approach.
Fejfar Antonín - One of the best experts on this subject based on the ideXlab platform.
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ANNEALING OF POLYCRYSTALLINE THIN FILM SILICON SOLAR CELLS IN WATER VAPOUR AT SUBATMOSPHERIC PRESSURES
'Czech Technical University in Prague - Central Library', 2017Co-Authors: Pikna Peter, Píč Vlastimil, Benda Vítězslav, Fejfar AntonínAbstract:Thin film polycrystalline silicon (poly-Si) solar cells were annealed in water vapour at pressures below atmospheric pressure. PN junction of the sample was contacted by measuring probes directly in the pressure chamber filled with steam during passivation. Suns-VOC method and a Lock-in detector were used to monitor an effect of water vapour to VOC of the solar cell during whole passivation process (in-situ). Tested temperature of the sample (55°C – 110°C) was constant during the procedure. Open-circuit voltage of a solar cell at these temperatures is lower than at room temperature. Nevertheless, voltage response of the solar cell to the light flash used during Suns-VOC measurements was good observable. Temperature dependences for Multicrystalline Wafer-based and polycrystalline thin film solar cells were measured and compared. While no significant improvement of thin film poly-Si solar cell parameters by annealing in water vapour at under-atmospheric pressures was observed up to now, in-situ observation proved required sensitivity to changing VOC at elevated temperatures during the process