This Public Research Seminar was on 26 April 2012
Classification and Investigation of Recombination Active Defects in Multicrystalline Silicon Solar Cells
Location: UNSW Building H6 – Tyree Energy Technologies Building - Room G17
Time: 12pm - 1pm
All multicrystalline silicon (mc-Si) solar cells suffer from recombination active defect structures. Recombination active defects in solar cells made from pure as well as from upgraded metallurgical grade Si feedstock are limiting the solar efficiency and electrical breakdown behaviour. Therefore it is of utmost importance to understand the cause and the physical mechanism of recombination and pre-breakdown processes at these defects. Since a mc-Si solar cell has a large number of defects it is mandatory to classify the different defect before investigation. In this seminar a classification of recombination active defects in mc-Si solar cells based on previous studies is presented. Two types of recombination active defects can be clearly distinguished already on a macroscopic scale. For a more detailed understanding the classification was also performed on microscopic scale. It is shown that defect types observed on a macroscopic scale could also be directly related to structures on a microscopic scale; however, a third defect type had to be introduced. The microscopic investigations allow us to establish an exact relation of electrical, structural and chemical information. One defect type could be clearly correlated to metal precipitates located at defect structures of the underlying wafer explaining additionally the observed pre-breakdown behaviour at these defect structures. It is also shown that this defect type is strongly influenced by the solar cell process. Based on these results a model for the different classified types will be proposed explaining the observed recombination and pre-breakdown behaviour. The knowledge obtained can be reversibly interconnected to the macroscopic investigation on an industrial level to work on a solution to avoid these problems.