Low cost production of crystalline silicon thin films for solar cells by CVD process with closed gas recycling.

采用封闭气体回收的 CVD 工艺低成本生产太阳能电池用晶体硅薄膜。

基本信息

批准号：
15206086
负责人：
OKABE Fumio
金额：
$ 30.87万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2005
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15206086/
关键词：
crystalline silicon solar cells silicon supply reactant gas recycling high yield process chemical vapor deposition physical vapor deposition monocrystalline silicon thin films epitaxial lift-off 太陽電池 CVD エピタキシャル成長クロロシラン急速蒸着法エピ

项目摘要

Large-scale photovoltaic power generation is essential to realize future clean energy systems. The bulk silicon type is promising owing to the abundant resource and excellent stability and safety of silicon. This type now accounts for 80- 90 % of the solar cells. High purity silicon is supplied from the semiconductor industry, and the amount of supply is now limiting the further enhancement of solar cell production. In this project, large-scale, low-cost production of solar cells was studied.Silicon substrates are now industrially fabricated by slicing multi/monocrystalline silicon ingots, and an amount of silicon equivalent to about 500 μm thickness is consumed for each substrate. Substitution of substrates for thin films of 10 μm thickness can be a break through for scale enhancement and cost reduction of the solar cell production. We thus studied the epitaxial lift-off (ELO) method, in which a sacrificial layer and a monocrystalline silicon thin film are successively grown on a mono … More crystalline silicon wafer successively, the thin film and the wafer are separated by etching the sacrificial layer, and the thin film is used as the photovoltaic layer and the wafer is repeatedly used in this ELO process.In the ELO process, the epitaxial growth method of the monocrystalline silicon photovoltaic layer is very important. Chemical vapor deposition (CVD) is usually used to grow micrometer-thick epitaxial films, but the utilization ratio of the chlorosilane source gases is small. Chlorosilanes are practically synthesized by reacting metallurgical grade silicon with hydrogen chloride. By recycling the outlet gas of CVD reactor into the reactor of chlorosilane synthesis, an ideal process can be realized in which metallurgical grade silicon is converted into monocrystalline silicon thin films with a minimal material loss. Literature survey of the current production process of chlorosilanes and experimental investigations of the reaction rate processes of chlorosilane synthesis and Si-CVD were performed in parallel, and feasibility of this "CVD process with closed gas recycling" was examined. But the problems came out such as possible contaminations into silicon thin films and degradation of the sacrificial layer used in ELO process. On the other hand, physical vapor deposition (PVD) was suggested effective in the ELO process. Based on a new concept of rapid vapor deposition (RVD), a silicon epitaxial growth rate as large as 10μm/min was confirmed at the substrate temperatures of 800-1000℃.By coupling ELO and RVD processes, we succeeded to lift-off 5-10μm thick monocrystalline silicon thin films of a limited areal size. This is an achievement leading to the solution of the high-purity silicon shortage and the realization of large-scale, low-cost solar cell production. Less

大规模光伏发电是实现未来清洁能源系统的关键，体硅类型凭借其丰富的资源和优良的稳定性和安全性，目前占太阳能电池的80-90%。硅由半导体行业供应，目前供应量限制了太阳能电池产量的进一步提高。在该项目中，研究了太阳能电池的大规模、低成本生产。硅基板现在通过切片进行工业化制造。多晶/单晶硅锭，每个基板消耗的硅量相当于约500μm厚的薄膜，可以说是太阳能电池生产规模化和成本降低的突破。因此，我们研究了外延剥离（ELO）方法，其中牺牲层和单晶硅薄膜连续生长在单晶硅晶片上随后，通过刻蚀牺牲层将薄膜和晶圆分离，并在该ELO工艺中重复使用薄膜作为光伏层和晶圆。在ELO工艺中，单晶硅的外延生长方法光伏层非常重要，通常采用化学气相沉积（CVD）来生长微米厚的外延薄膜，但氯硅烷源气体的利用率较小。氯硅烷实际上是通过冶金级硅与氯化氢反应合成的，将CVD反应器的出口气体回收到氯硅烷合成反应器中，可以实现用最少的材料将冶金级硅转化为单晶硅薄膜的理想工艺。对现有氯硅烷生产工艺进行文献调查，同时对氯硅烷合成和Si-CVD反应速率过程进行实验研究，并探讨其可行性。研究了“封闭式气体回收CVD工艺”，但出现了硅薄膜可能受到污染以及ELO工艺中使用的牺牲层退化等问题。另一方面，物理气相沉积（PVD）被认为是有效的。基于快速气相沉积（RVD）的新概念，在800-1000℃的衬底温度下确认了硅外延生长速率高达10μm/min。通过RVD工艺，我们成功剥离了5-10μm厚的有限面积的单晶硅薄膜，解决了高纯硅短缺问题，实现了大规模、低成本的太阳能。细胞产量较少