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The investigation of different selective emitter (SE) approaches [1-3] is a current trend in solar cell manufacturing. The incorporation of a local high phosphorous doping underneath the front contact grid allows for the use of high-sheet resistance illuminated emitters that combine low recombination and improved blue response. Further efficiency increase compared to the standard screen-printed solar cell is achieved via plated contacts [4-5] that feature better aspect ratio and optical properties [6], higher line conductivity and smaller width [5] compared to screen-printed contacts. In this paper we present detailed technological requirements for next-generation front side metallization as well as experimental results of the RENA high-efficiency metallization cluster consisting of Laser Chemical Processing (LCP) and Ni-Ag light-induced plating (LIP). It becomes clear that efficiency on cell level is not the only figure of merit for a successful product and that the co mbination of SE with plating has a much higher potential for increasing cell efficiency than the metallization of SE via screen-printing

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The anodic oxidation of formic acid has been investigated on platinum black electrodes in 5N sulfuric acid. The data presented pertain to the activation controlled process under approximately steady state conditions at four temperatures between 25 ~ and 90~ Tafel plots appear to have significant slopes, and the correlation of these slopes with experimentally measured electrode coverages supports the hypothesis of two distinct electrochemical oxidation mechanisms, advanced by other workers.The electrochemical oxidation of formic acid has been studied by many workers (1-6), the most recent paper being one by Breiter (7) who studied electrode coverage and current-voltage relationships at ambient temperature with bright platinum electrodes. In the present work, coverage measurements and current-voltage data were obtained at four temperatures, 25 ~ 45 ~ 70 ~ and 90~ using platinized platinum electrodes in a 5N H2SO4-1M HCOOH solution.Although perchloric acid has frequently been used as an electrolyte for such work, it becomes an oxidizing agent at higher temperatures. With sulfuric acid, this effect is smaller.The choice of concentration of formic acid was based on the observation that the current in all potential regions ceased to be dependent on concentration somewhere between 0.5 and 1.0 molar on the type of electrodes investigated and at the highest temperatures employed. This fact was taken to indicate the establishment of activation, rather than diffusion-controlled rates of reaction. This region of concentration is also that reported by Breiter (8) and Pavela (2) to be necessary to achieve saturated coverage of platinum electrodes in solutions of methanol. It may be noted in passing that the maximum current densities obtainable in these systems at moderate concentrations are considerably in excess of the limiting currents predicted by steady state diffusion calculations because of the convective stirring due to the evolution of carbon dioxide.In view of Breiter's statement (for methanol) that extremely small amounts of hydrogen were observed on bright platinum electrodes at open circuit, while significant amounts of hydrogen have been measured in this work, the difference in the type of electrode is an important one. Schwabe (9) and others have measured the rate of heterogeneous decomposition of formic acid, using platinum black catalysts. ExperimentalMaterials and electrodes.--Reagent grade formic acid (98 Jr %, Eastman) and sulfuric acid (Baker) were used throughout the work.Platinized platinum electrodes were prepared from 0.003 in. platinum sheet. The plating solution was 1.7N HC1 containing 2.4 weight per cent Pt (as HfPtC16, Bishop) and a trace of lead acetate. Deposition of the black was carried out simultaneously on all electrodes at 10 ma/cm 2 for 3 min followed by 50 ma/cm e for 2 min. The resulting surfaces were smooth and uniformly black. The geometric area of the electrodes was 2 cm 2 for the work at room temperature but was decreased for the work at higher temperatures in order to provide currents...

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