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New Method of Preparation of Polycrystalline Silicon Thin Films for High-Efficiency and Low-Cost Solar Cells

高效低成本太阳能电池多晶硅薄膜制备新方法

基本信息

批准号：
07458106
负责人：
NAKATO Yoshihiro
金额：
$ 4.48万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07458106/
关键词：
Polycrysalline silicon Porous silicon Ultrafine metal particle Electrodeposition Fused salt electrolyte Current oscillation Solar cell New junction 多結晶シリコン薄膜常温溶融塩振動現象

项目摘要

Research has been made for the purpose of (1) preparing polycrystalline silicon (Si) thin films by a new electrochemical method and (2) fabrication a high-efficiency and lowcost solar cell of a new type by development of a new junction suitable for use of such polycrystalline Si thin films. A LiCl-KCl eutectic melt at ca. 450ﾟC was used as an electrolyte, and silicon tetrachloride was electrochemically reduced and deposited on a single-crystal Si wafer or a polycrystalline Ni plate as the cathode (and substrate). Scanning electron micrographs and X-ray photoelectron spectroscopy showed that polycrystalline Si thin films were really deposited, but the films were inhomogeneous and deposited only near the upper edge of an electrolyte meniscus on the cathode, probably due to very low solubility of SiCl_4 in the electrolyte. This problem has been solved later by using an organic salt such as n-butylpyridinium chloride as the electrolyte. Basic studies on the mechanism of Si deposition has been made. First, the redox potential for SiCl_4 reduction was determined to be -0.5 V vs.Ag/Ag^+. Next, the mechanism of a current oscillation, found for reduction current corresponding to Si deposition was studied. It has been concluded that progress of the Si-depositing reaction changes the chemical structure of the Si surface, which alters the interfacial tension and hence the height of an electrolyte meniscus, and this causes the current oscillation. The Si surface modified with ultrafine metal particles has been studied as a new junction suitable for use of polycrystalline Si thin films. The deposition of ultrafine platinum particles not only on singlecrystal Si but also multicrystalline Si wafers showed that this method of junction formation is effectively applicable to polycrystalline Si thin films.

本研究的目的是：(1)利用新的电化学方法制备多晶硅（Si）薄膜；(2)通过开发适合多晶硅薄膜使用的新型结，制备高效率、低成本的新型太阳能电池。采用约450°C的LiCl-KCl共晶熔体作为电解液，将四氯化硅电化学还原并沉积在单晶硅片或多晶Ni板上作为阴极（和衬底）。扫描电镜和x射线光电子能谱分析表明，沉积了多晶硅薄膜，但薄膜不均匀，仅沉积在阴极电解质半月板的上边缘附近，这可能是由于SiCl_4在电解质中的溶解度很低所致。这个问题后来通过使用一种有机盐如氯化正丁基吡啶作为电解质得到了解决。对硅沉积机理进行了基础研究。首先，确定SiCl_4还原的氧化还原电位为-0.5 V vs.Ag/Ag^+。其次，研究了与硅沉积相对应的还原电流振荡的机理。沉积反应的进行改变了硅表面的化学结构，改变了界面张力，从而改变了电解质半月板的高度，从而引起了电流的振荡。研究了用超细金属粒子修饰的硅表面作为一种适合多晶硅薄膜使用的新结。超细铂粒子不仅在单晶硅上沉积，而且在多晶硅片上沉积，表明这种结形成方法有效地适用于多晶硅薄膜。