Growth of crystalline silicon for solar cells: Noncontact crucible method

Abstract

The noncontact crucible (NOC) method has the potential to be an advanced cast method. It is effective in obtaining Si single ingots with large diameter and volume using cast furnace, and solar cells manufactured with Si obtained this way have high yield and high conversion efficiency. Several novel characteristics of this method are explained based on the existence of a large low-temperature region in a Si melt, which is key to realize its enclosing potential as follows. The largest diameter ratio of 0.9 was obtained by expanding the low-temperature region in the Si melt. For p-type solar cells, the highest of 19.14% and the average conversion efficiencies of 19.0% were obtained for the NOC wafers, using the same solar cell structure and process to obtain the conversion efficiency of 19.1% for a p-type Czochralski (CZ) wafers. The present method realized solar cells with conversion efficiency and yield as high as those of CZ solar cells using cast furnace for the first time. The latest information about the growth of Si ingots using the NOC method is explained.