Development of a three-dimensional numerical model of grain boundaries in highly doped polycrystalline silicon and applications to solar cells

We have developed a three-dimensional numerical model of grain boundaries to simulate the electrical properties of polycrystalline silicon with doping densities larger than approximately 5x10(17) cm(-3). We show that three-dimensional effects play an important role in quantifying the minority-carrier properties of polycrystalline silicon. Our simulations reproduce the open-circuit voltage of a wide range of published experiments on thin-film silicon p-n junction solar cells, choosing a velocity parameter for recombination at the grain boundaries, S, in the order of 10(5)-10(6) cm/s. The simulations indicate that, although S has been reduced by one order of magnitude over the last two decades, improvements in the open-circuit voltage have mainly been achieved by increasing the grain size. A few options are proposed to further reduce S. (C) 2002 American Institute of Physics.