Texturization control for fabrication of high efficiency mono crystalline si solar cell
We studied the texturization mechanism of mono crystalline silicon wafer using some alternative additives. We successfully controlled the texture size with change of concentration of KOH in the etchant. We also proposed one appropriate model of role of additives in texturization process. In our proposed mechanism, the additives should play a role as micro-mask when the micro pyramid is formed and the texturization process should be dominated by the correlation of etching rate and adhesion and desorption rate of additives. We also fabricated solar cells with several texture sizes and evaluated them. The decrease of F.F. with the decrease of texture size was mainly caused by the increase of Rs and this result suggested that we had to optimize the screen printing and firing conditions for the small texture. In addition, there are thick damaged layer on the top and bottom of texture, and these damaged layer cause the deterioration of cell efficiency with texture miniaturization. Reduction of the damage is important to realize high efficiency solar cell using miniaturized texture.
Effectiveness of anisotropic etching of silicon in aqueous alkaline solutions
Abstract Optical effectiveness of anisotropic etching of (1 0 0) silicon in inorganic alkaline solution has been studied from the view point of its application in commercial silicon solar cells. The damage caused by ID saw or wire saw during slicing of the wafer is required to be removed for fabrication of solar cells. The etch rates for removal of the surface damages for boron doped Czochralski wafers of 1–2 Ω cm resistivity in 20% NaOH solution at 80°C was measured and was found to be ∼1.4 μm/min. After the damage removal, texturisation was obtained in 2% NaOH solution buffered with isopropyl alcohol at 80°C. An optical effectiveness parameter feff,λ was defined and its value was estimated from the study of reflectivity and topography of the wafers textured for different durations of time. The kinetics of anisotropic etching was studied which indicated that growth of pyramids begins at preferential sites which may arise due to crystalline defects or wetting. Silicon solar cells have been realized by standard process involving phosphorous diffusion and vacuum evaporated front and back contacts. The value of optical effectiveness parameter is found to have a direct correlation with the improvement in short circuit current density of the textured cells.
Growth and Characterization of β-RDX Single-Crystal Particles
1,3,5-Trinitrohexahydro-s-triazine (RDX) single-crystal particles crystallized in the β phase have been successfully grown by sublimation–recrystallization. Synchrotron X-ray diffraction results confirm that the recrystallized products are β-RDX single crystals. Compared to the traditional solution deposition methods, the sublimation method used in this work breaks through the mass limitations during the growth of β-RDX. The distribution of α- and β-RDX on different substrates reveals that hydrophilic substrates are prone to grow β-RDX single crystals and that hydrophobic substrates prefer α-RDX single crystals. The sublimation rate dominates the growth of pure β-RDX. The mechanisms of the phase transition from β-RDX to α-RDX during the process of sublimation–recrystallization have been studied. The current results can promote the potential application of β-RDX in the propellant, explosives, and military fields.