Improving the Quality of the Deteriorated Regions of Multicrystalline Silicon Ingots during General Solar Cell Processes

The behavior of wafers and solar cells from the border of a multicrystalline silicon(mc-Si)ingot,which contain deteriorated regions,is investigated.It is found that the diffusion length distribution of minority carriers in the cells is uniform,and high efficiency of the solar cells(about 16%)is achieved.It is considered that the quality of the deteriorated regions could be improved to be similar to that of adjacent regions.Moreover,it is indicated that during general solar cell fabrication,phosphorus gettering and hydrogen passivation could significantly improve the quality of deteriorated regions,while aluminum gettering by RTP could not.Therefore,it is suggested that the border of a me-Si ingot could be used to fabricate high efficiency solar cells,which will increase me-Si utilization effectively.

Effects of Co₂O₃on Crystallization and Colorization of Lithium Aluminosilicate Glass Ceramics

The effects of Co2O3 on the crystallization and colorization of lithium aluminosilicate glass ceramic were investigated by using differential thermal analysis (DTA), X-ray diffractometry (XRD) and scanning electron microscope (SEM). The results showed that the introduction of Co2O3 not only changed the color of lithium aluminosilicate glass but also affected its crystallization by increasing the crystallizing maximum peak temperature (Tp) and weakening the crystallization ability. In addition, the color of LAS glass ceramics could be achieved by controlling the suitable Co2O3 and appropriate crystallization temperature.

Effect of Powder Particle Size on the Fabrication of Ti-6Al-4V Using Direct Laser Metal Deposition from Elemental Powder Mixture

Direct LMD （laser metal deposition） was used to fabricate thin-wall Ti-6Al-4V using the powder mixture of Ti-6 wt.%Al-4 wt.%V. SEM （scanning electron microscopy）, OM （optical microscopy） and EDS （energy dispersive spectroscopy） were employed to examine the chemical composition and microstructure of the as-deposited sections. Vickers hardness tests were then applied to characterize the mechanical properties of the deposit samples which were fabricated using pre-mixed elemental powders. The EDS line scans indicated that the chemical composition of the samples was homogenous across the deposit. After significant analysis, some differences were observed among two sets of deposit samples which varied in the particle size of the mixing Ti-6wt.%Al-4wt.%V powder. It could be found that the set with similar particle number for Ti, Al and V powder made composition much more stable and could easily get industry qualified Ti-6Al-4V components.

Denuded Zone Formation in Germanium Codoped Heavily Phosphorus-Doped Czochralski Silicon

The formation of a denuded zone(DZ)by conventional furnace annealing(CFA)and rapid thermal annealing(RTA)based denudation processing is investigated and the gettering of copper(Cu)atoms in germanium co-doped heavily phosphorus-doped Czochralski(GHPCZ)silicon wafers is evaluated.It is suggested that both a good quality defect-free DZ with a suitable width in the sub-surface area and a high density bulk micro-defect(BMD)region could be formed in heavily phosphorus-doped Czochralski(HPCZ)silicon and GHPCZ silicon wafers.This is ascribed to the formation of phosphorus-vacancy(P-V)related complexes and germanium-vacancy(GeV)related complexes.Compared with HPCZ silicon,the DZ width is wider in the GHPCZ silicon sample with CFA-based denudation processing but narrower in the one with two-step RTA pretreatments.These phenomena are ascribed to the enhancing effect of germanium on oxygen out-diffusion movement and oxygen precipitate nucleation,respectively.Furthermore,fairly clean DZs near the surface remain in both the HPCZ and GHPCZ silicon wafers after Cu in-diffusion,except for the HPCZ silicon wafer which underwent denudation processing with a CFA pretreatment,suggesting that germanium doping could improve the gettering of Cu contamination.

Random lasing in an Anderson localizing optical fiber

A directional random laser mediated by transverse Anderson localization in a disordered glass optical fiber is reported.Previous demonstrations of random lasers have found limited applications because of their multi-directionality and chaotic fluctuations in the laser emission.The random laser presented in this paper operates in the Anderson localization regime.The disorder induced localized states form isolated local channels that make the output laser beam highly directional and stabilize its spectrum.The strong transverse disorder and longitudinal invariance result in isolated lasing modes with negligible interaction with their surroundings,traveling back and forth in a Fabry–Perot cavity formed by the air–fiber interfaces.It is shown that if a localized input pump is scanned across the disordered fiber input facet,the output laser signal follows the transverse position of the pump.Moreover,a uniformly distributed pump across the input facet of the disordered fiber generates a laser signal with very low spatial coherence that can be of practical importance in many optical platforms including image transport with fiber bundles.

Realizing the thinnest hydrodynamic cloak in porous medium flow

Transformation mapping theory offers us great versatility to design invisible cloaks for the physical fields whose propagation equations remain invariant under coordinate transformations.Such cloaks are typically designed as a multi-layer shell with anisotropic material properties,which makes no disturbance to the external field.As a result,an observer outside the cloak cannot detect the existence of this object from the field disturbances,leading to the invisible effect in terms of field prorogation.In fact,for many prorogating fields,at a large enough distance,the field distortion caused by an object is negligible anyway;thus,a thin cloak is desirable to achieve near-field invisibility.However,a thin cloak typically requires more challenging material properties,which are difficult to realize due to the huge variation of anisotropic material parameters in a thin cloak region.For a flow field in a porous medium,by applying the bilayer cloak design method and integrating the inner layer with the obstacle,we successfully reduce the anisotropic multi-layer cloak into an isotropic single-layer cloak.By properly tailoring the permeability of the porous medium,we realize the challenging material parameters required by the ultrathin cloak and build the thinnest shell-shaped cloak of all physical fields up to now.The ratio between the cloak’s thickness and its shielding region is only 0.003.The design of such an ultrathin cloak may help to achieve the near-field invisibility and concealment of objects inside a fluid environment more effectively.