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B implanted emitters are investigated in the back junction cell configuration and their material properties are tested in double side implanted Si wafers. B has been implanted at 5 keV at various dose conditions varying from 1 × 1014 up to 3 × 1015 at./cm2 and activated at 1000°C for 10 min. N‐type 8 × 8 cm2 mono‐crystalline cells are fabricated and measured. Both fill factor and efficiency increase for high‐B doses. However, at 1015 at./cm2 B dose the Voc drops, which is in agreement with lifetime degradation in the wafer. Defect evolution simulations of BnIm clusters formation is correlated with lifetime degradation. Copyright © 2011 John Wiley & Sons, Ltd.

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Abstract-This paper proposes a novel concept for integrating ultrathin solar cells into modules. It is conceived as a method for fabricating solar panels starting from back-contact crystalline silicon solar cells. However, compared to the current state of the art in module manufacturing for back-contact solar cells, this novel concept aims at improvements in performance, reliability, and cost through the use of an alternative encapsulant, namely silicones as opposed to ethylene vinyl acetate, an alternative deposition technology, being wet coating as opposed to dry lamination; and alternative module-level metallization techniques, as opposed to cell-level tabbing-stringing or conductive foil interconnects. The process flow is proposed, and the materials and fabrication technologies are discussed. As the durability of the module, translated into the module's lifetime, is very important in the targeted application, namely solar cell modules, modeling and reliability testing results and considerations are presented to illustrate how the experimental development process may be guided by experience and theoretical derivations. Finally, feasibility is demonstrated in some first proofs of the concept, and an outlook is given pointing out the direction for further research.

We present a new wafering method for the production of ultra-thin crystalline silicon. This new lift-off process, named SLIM-cut (for Stress-induced Lift-off Method), requires only the use of a screen-printer and a belt furnace; no ion-implanted, porous layer or additional thickening by epitaxy is needed to obtain high quality wafers in the thickness range of 50 IJm without kerf loss. We deposit on a thick substrate a layer with mismatched coefficient of thermal expansion with respect to the substrate (for instance a metal layer). Upon cooling, the differential contraction induces a large stress field, which is released by the initiation and the propagation of a crack parallel to the surface. The concept has already been demonstrated successfully on both single and multi-crystalline silicon.

N‐type back‐junction back‐contact (BJ–BC) silicon solar cells have been successfully introduced in industry by Sunpower with efficiencies up to 23.4% and are being investigated by several research groups. For such n‐type bulk Si solar cells, the formation of the p+ emitter is still an issue. A traditional method is boron diffusion, which needs high temperature processes to form the emitter and to remove the silicate glass boron skin. In recent years, people have shown excellent results on n‐type front contact rear junction cells with a screen‐printed Al‐alloyed emitter. In this work, we demonstrate the use of such emitters on n‐type BJ–BC silicon solar cells. Different pitch sizes and emitter fractions have been studied. Clear trends of the short‐circuit current densities have been observed. Light beam induced current technique is used to investigate this phenomenon. Different front surface field (FSF) profiles were applied to our cells. The shallower FSF with a lower surface doping concentration results in lower front surface recombination, which results in the best cell performance. Efficiencies of 19.1% under 1 Sun on BJ–BC solar cells with an aperture area of 2 cm × 2 cm have been achieved on n‐type FZ and CZ silicon wafers. Good short‐circuit current densities and fill factors have been obtained. Compared to the boron‐diffused emitter BJ–BC solar cells, relatively low open‐circuit voltages were obtained. Better quality emitter with more effective cleaning process steps and passivation layers have been developed, to result in a further increase in cell efficiency in the future work. Copyright © 2010 John Wiley & Sons, Ltd.

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