Separated striations in n-type Czochralski silicon solar cells

Currently, in the photovoltaic industry, the market share of n-type monocrystalline silicon is rapidly increasing. However, during mass production, striation defects characterized by concentric circles significantly impact the efficiency of solar cells. In this paper, we investigate the properties and origins of striations in n-type Czochralski silicon solar cells. These striations, occurring in wafers with an oxygen concentration below 7 × 1017 cm−3, are shown to potentially cause an efficiency degradation up to 0.86% absolute. Through an array of techniques, including photoluminescence, optical microscopy (OM), electron beam induced current (EBIC), and Fourier Transform Infrared Spectroscopy, this work demonstrates that such defects primarily form after the thermal treatment processes in the manufacturing of solar cells and indirectly proves that these defects are related to the precipitation behavior of oxygen. Notably, traditional methods of post-polishing and etching followed by OM and EBIC technique failed to detect these defects. Therefore, the indirect characterization methods designed in this study hold significant referential value.