Study of Dislocations in the Minicrystallized Regions in Multicrystalline Silicon Grown by the Directional Solidification Method

Directionally solidified multicrystalline silicon (mc-Si)-based solar cells have dominated the global photovoltaic market in recent years. The photovoltaic performance of mc-Si solar cells is strongly influenced by their crystalline defects. The occurrence of minicrystallization results in much smaller grain size and, therefore, a larger number of grain boundaries in mc-Si ingots. Dislocations in the minicrystallized regions have been rarely investigated in the literature. In this work, optical microscopy was used to investigate dislocations in the mincrystallized regions in mc-Si ingots grown by the directional solidification method. The distribution of dislocations was found to be highly inhomogeneous from one grain to another in the mincrystallized regions. High inhomogeneity of dislocation distribution was also observed in individual grains. Serious shunting behavior was observed in the mc-Si solar cells containing minicrystallized regions, which strongly deteriorates their photovoltaic properties. The shunting was found to be highly localized to the minicrystallized regions.