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.
The Open Mobile Alliance: Delivering Service Enablers for Next-Generation Applications
Apractical overview of OMA specifications and how they enable mobile multimedia services & much more ! The Open Mobile Alliance (OMA) is an industry forum, which develops open specifications to help in the creation of applications and services to be deployed over converged networks. The alliance is the leading industry forum for generating market-driven specifications for interoperable mobile service enablers that facilitate global user adoptions of mobile multimedia services. Members include traditional wireless industry segments, such as mobile operators mobile operators (e.g. AT&T, China Mobile, Orange, Sprint Nextel, T-Mobile, Telefonica, Vodafone), equipment and mobile systems manufacturers (e.g. Alcatel-Lucent, Ericsson, Motorola, Nokia, Philips, Samsung, Siemens, Sony-Ericsson), and Information Technology vendors (e.g. BEA Systems, IBM, Microsoft, Oracle Corporation, Sun Microsystems and NEC). Since its formation in 2002, the OMA has made significant progress in areas such as push-to-talk over cellular, device management, presence and group management, and messaging. The Open Mobile Alliance: Provides a comprehensive overview of the service enablers published by the OMA, tying together all the different piece parts developed by the individual working groups Offers a thorough introduction to the OMA Service Environments (OSE) and the specification process for enabling technologies. Discusses enablers for services such as gaming, IMS, Parlay, mobile broadcast and web services. Contains contributions from all stakeholders in the mobile application value chain. The Open Mobile Alliance Alliance is an invaluable resource for OMA members, product managers, network architects and planners, standards managers, standards engineers and IT professionals. Advanced Students and lecturers on mobile application development and standardization courses will also find this book of interest."The success of OMA is due to its individual members' contributions, and this book is testament to their hard work. The individual members' efforts and the authors of this book are to be congratulated on their magnificent achievements." Mark Cataldo, Senior Advisor, Orange SA, OMA Technical Plenary Chairman