Abstract Graphite crucibles are potentially interesting for the directional solidification processing of photovoltaic silicon, because, contrarily to standard silica crucibles, they can be used many times. In the present work, two types of graphite crucibles are studied: i) graphite directly coated with the Si3N4 powder classically used as a releasing layer for standard silica crucibles, and ii) graphite protected by a dense SiC layer before deposition of the releasing coating. In both cases, spontaneous detachment of the silicon ingot is observed to occur during cooling. Results are given and discussed concerning the impurities introduced in the silicon during the melting-solidification cycle, as well as their consequences on the photo-electrical characteristics of silicon. These results are compared with those obtained using the standard silica crucible. It is shown that re-useable SiC protected graphite crucibles lead to the same performances as standard silica. Reproducible results are found after four runs with the same crucible, and no degradation of the crucible is observed.

中文翻译：

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可重复使用石墨坩埚中光伏硅的定向凝固

摘要 石墨坩埚对于光伏硅的定向凝固加工具有潜在的意义，因为与标准二氧化硅坩埚相反，它们可以多次使用。在目前的工作中，研究了两种类型的石墨坩埚：i）直接涂有 Si3N4 粉末的石墨，通常用作标准二氧化硅坩埚的脱模层，以及 ii）在沉积脱模涂层之前由致密的 SiC 层保护的石墨。在这两种情况下，都观察到在冷却过程中会发生硅锭的自发分离。给出并讨论了在熔化-凝固循环期间引入硅中的杂质及其对硅光电特性的影响的结果。将这些结果与使用标准二氧化硅坩埚获得的结果进行比较。结果表明，可重复使用的 SiC 保护石墨坩埚与标准二氧化硅具有相同的性能。使用相同的坩埚运行四次后发现了可重现的结果，并且没有观察到坩埚的降解。