발간논문

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We have synthesized core-shell structured nanocrystals based on chalcopyrite-type Cu0.2InS2. The photoluminescence of the nanocrystals shows a significant blueshift in the emission wavelength by shell capping with ZnS layers. This shift can be explained with the compressive stress to core nanocrystals applied by the formation of a ZnS shell layer with a large lattice mismatch with the core. In this study, the emission wavelength could be tuned by changing the composition of the shell layers. Nanocrystals with emission wavelength ranging from 575 nm through 630 nm were synthesized by varying the portion of cadmium compared with zinc in the shell layers.

keyword : nanostructured materials, chemical synthesis, optical properties, transmission electron microscopy (TEM), quantum dot

The formation of front metal contact silicon solar cells is required for low cost, low contact resistance to silicon surfaces. One of the available front metal contacts is Ni/Cu plating, which can be mass produced via asimple and inexpensive process. A selective emitter, meanwhile, involves two different doping levels, with higher doping (≤30 Ω/sq) underneath the grid to achieve good ohmic contact and low doping between the grid in order to minimize the heavy doping effect in the emitter. This study describes the formation of a selective emitter and a nickel silicide seed layer for the front metallization of silicon cells. The contacts were thickened by a plated Ni/Cu two-step metallization process on front contacts. The experimental results showed that the Ni layer via SEM (Scanning Electron Microscopy) and EDX (Energy dispersive Xray spectroscopy) analyses. Finally, a plated Ni/Cu contact solar cell displayed efficiency of 18.10% on a 2×2 cm2, Cz wafer.

keyword : solar cells, plating, conductivity, scanning electron microscopy(SEM), Ni/Cu front metal

The microstructures and mechanical properties of roll-bonded STS439/Al1050/STS304 clad materials were investigated after an annealing process at various temperatures. Interfacial layer was developed at the STS439/Al1050 and Al1050/ STS304 interfaces at 550℃. STS439/Al1050/STS304 clad metals fractured suddenly in a single step and the fracture decreased with increasing annealing temperatures at 450℃. After annealing at 550℃, samples fractured in three steps with each layer fracturing independently. Interfacial layers formed at 550℃ with a high Vickers microhardness were found to be brittle. During tensile testing, periodic parallel cracks were observed at the interfacial reaction layer. Observed micro-void between Al1050 and the interfacial layer was found to weaken the Al1050/reaction layer interface, leading to the total separation between Al1050 and the reaction layer.

keyword : stainless steel, aluminum, clad sheet, interface properties, compound Layer, annealing, mechanical properties