DESIGN OF A BIFACIAL SI SOLAR CELL WITH UNIFORMLY DOPED B IMPLANTED AND P THERMAL DIFFUSED LAYERS

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DESIGN OF A BIFACIAL SI SOLAR CELL WITH UNIFORMLY DOPED B IMPLANTED AND P THERMAL DIFFUSED LAYERS

Si bifacial cells have been used extensively in space [1]. The ability to generate additional energy due to the earth'salbedo illuminating the back of the cell made the bifacial cells promising for low earth orbit. Bifacial n+-p-p+ cellswere produced by technology based on the combination of thermal P diffusion for n+ emitter doping and B ionimplantation with subsequent annealing for p+ layer doping [2].This design and basic elements of the fabrication technology can also have increasing terrestrial applications dueto the development of high throughput ion implant tools [3]. p+ layer doping using ion implantation procedure is akey component of cell fabrication technology. Parameters of this process such as ion dose and annealingconditions (time/temperature, gas atmosphere, cap layers etc.) are of significant interest for optimization offabrication processing and improvement of solar cell performance. In addition to introducing electrically activedoping atoms as well as defect formation in the doped layer, another effect can appear as a result of ionimplantation – creation of a defect layer behind the implanted layer. Former as well as new data on conditions forminimization of, or avoiding defect layer formation in the base region will be analyzed.Surface passivation of the p+ layer is an important part of cell fabrication technology. The significance of thecharges, trapped by the passivation layer for surface recombination suppressing, needs to be evaluated.B implantation and its studying can be applied not only for p- but also for n-type starting Si. Superiority of theback junction compared to the front junction design ought to be estimated.Effects of implantation dose, starting Si parameters and measurement conditions, on solar cell base recombination,surface recombination suppressing by thermal oxidation and comparative evaluation of back vs. front junctiondesign are the subjects of this presentation. For the full article>>

 

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