Twenty years crystal growth of solar silicon: My serendipity journey

The past two decades have been a transformative era for solar silicon crystal growth, especially in the competition between multi-crystalline silicon (Multi-Si) and mono-crystalline silicon (Mono-Si). As a critical sector of the solar photovoltaic (PV) industry, the demand for this crucial material has surged exponentially, expanding over a thousand-fold. This remarkable increase has led to an accumulative deployment of silicon solar panels, which now approach a striking terawatt (TW), capturing over 95% of the global PV market share. Furthermore, the rapid advancements in crystal growth technology during this period have set an unprecedented historical benchmark. This paper reviewed our early effort in the hot-zone design of Czochralski (CZ) solar silicon and then discussed its recent advancements. In between, the small-grain high-performance multi-crystalline silicon (HPM-Si), which we proposed, and the mono-like silicon (ML-Si) were briefly introduced. Because of the much better ingot quality and growth yield, HPM-Si became the mainstream until 2018. Its market share peaked at more than 70% in 2017 but slid down quickly and was replaced by CZ silicon due to the emergence of diamond wire sawing (DWS); the CZ silicon was easier to cut, and its kerf loss was much less. Since then, the CZ ingot size has also started to increase quickly. The wafer size increased from 156 mm x 156 mm (M0) to 217 mm x 217 mm (M12+) in a few recent years; the increase in wafer area was almost doubled. Nowadays, the market share of CZ mono-Si is over 80%.