Continuously improving crystallization conditions and solar cell processes have lead to steadily increasing efficiencies of solar cells based on multicrystalline silicon. There is, however, still an efficiency gap between mono- and multicrystalline silicon amounting to 1-2 % (absolute) depending on the cell process used. Topographies of the local solar cell performance clearly reveal that the main contribution to this efficiency gap is due to recombination-active dislocations present in multicrystalline silicon. A further improvement of the efficiencies attainable with multicrystalline solar cells therefore is achievable by a reduction of the dislocation density. Dislocations originate from thermal stress that originates from temperature gradients inside a multicrystalline ingot during crystallization and cooling. In order to reduce this thermal stress and consequently the dislocation density we employ a numerical simulation routine, the so-called virtual crystallization furnace, for perfect control of the temperature distribution during the entire ingot fabrication process.