Abstract
The silicon material for photovoltaic (PV) industry demands high quality. It is known that dislocation clusters are among the foremost limiting effects on the minority carrier lifetime, and thus the PV efficiency. The high-perfomance multicrystalline Si (HPMC-Si) has proved to limit the abundance of these clusters due to a smaller grain size and a larger proportion of the random angle grain boundaries (RAGB). In this project, the focus
of this study is to find and understand the factors affecting the dislocation density at the nucleation stage. The ingots used in this thesis is made in a conventional quartz crucible coated with a Si 3 N 4 coating through directional solidification. Three different lateral positions, i.e., edge, corner and centre of the same ingot was examined. Vertical and horizontal cross-sections of each sample was studied and the combo scans for grain
boundary types and grain size was carried out using JEOL JSM 840A scanning electron microscope. The results prove that uniform, small grains and high RAGB are the characteristic features to get a low dislocation density in the ingot. There are many factors in the nucleation stage that play an important role and need to be controlled to obtain these features.
