OPTIMUM 2-DIMENSIONAL SHORT-CIRCUIT COLLECTION EFFICIENCY IN THIN MULTICRYSTALLINE SILICON SOLAR-CELLS WITH OPTICAL CONFINEMENT

The two-dimensional short-circuit AM1.5 collection efficiency is studi ed in thin multicrystalline silicon solar cells with optical confineme nt. The collection efficiency is calculated by linking an optical anal ytical generation profile with the two-dimensional collection probabil ity in pn junction solar cells. The calculations are carried out for v ariable grain boundary recombination velocity, cell thickness, grain w idth, diffusion length, and back surface recombination velocity. The r ole of optical confinement leading to a strong dependence of the colle ction efficiency on the cell thickness in very thin cells is confirmed . The optimum cell thickness for maximum collection efficiency increas es in cells with low back reflection or poor back surface passivation. Also, the optimum thickness in very thin cells increases significantl y with increasing the diffusion length. It is also found that the effe ct of grain boundary recombination is predominant if the cell thicknes s is larger than the diffusion length and if the diffusion length is l arger than half the grain width, especially, in cells with unpassivate d grain boundaries. On the other hand, back surface recombination domi nates the response in cells with unpassivated back surface if the thic kness is smaller than or comparable to the diffusion length. (C) 1998 Elsevier Science B.V. All rights reserved.