Studies of implanted boron emitters for solar cell applications

International audienceB 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 Â 10 14 up to 3 Â 10 15 at./cm 2 and activated at 10008C for 10 min. N-type 8 Â 8 cm 2 mono-crystalline cells are fabricated and measured. Both fill factor and efficiency increase for high-B doses. However, at 10 15 at./cm 2 B dose the V oc drops, which is in agreement with lifetime degradation in the wafer. Defect evolution simulations of B n I m clusters formation is correlated with lifetime degradation

Feasibility of using thin crystalline silicon films epitaxially grown at 165 °C in solar cells: A computer simulation study

We have previously reported on the successful deposition of heterojunction solar cells whose thin intrinsic crystalline absorber layer is grown using the standard radio frequency plasma enhanced chemical vapour deposition process at 165 °C on highly doped P-type (100) crystalline silicon substrates. The structure had an N-doped hydrogenated amorphous silicon emitter deposited on top of the intrinsic epitaxial silicon layer. However to form the basis of a solar cell, the epitaxial silicon film must be chiefly responsible for the photo-generated current of the structure and not the underlying crystalline silicon substrate. In this article we use detailed electrical-optical modelling to calculate the minimum thickness of the epitaxial silicon layer for this to happen. We have also investigated by modelling the influence of the a-Si:H/epitaxial-Si and epitaxial-Si/c-Si interface defects, the thickness of the epitaxial silicon layer and its volume defect density on cell performance. Finally by varying the input parameters and considering various light-trapping schemes, we show that it is possible to attain a conversion efficiency in excess of 13% using only a 5 micron thick epitaxial silicon layer

Efficiency (>15%) for thin-film epitaxial silicon solar cells on 70 cm2 area off spec silicon substrate using porous silicon segmented mirrors

We report on the beneficial use of embedded segmented porous silicon broad-band optical reflectors for thin-film epitaxial silicon solar cells. These reflectors are formed by gradual increase of the spatial period between the layer segments, allowing for an enhanced absorption of low energy photons in the epitaxial layer. By combining these reflectors with wellestablished solar cell processing by photolithography, a conversion efficiency of 15-2% was reached on 73 cm2 area, highly doped offspec multicrystalline silicon substrates. The corresponding photogenerated current densities (Jsc) were well above 31 mA/cm2 for an active layer of only 20 m