Thermodynamics of Phosphorus in Molten Silicon

熔融硅中磷的热力学

• 批准号: 07650866
• 负责人: SUZUKI Kichiya
• 金额: $ 1.41万
• 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 (C)
• 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-07650866/
• 关键词: Silicon; Phosphorus; Iron; Titanium; Solar Cell; Chemical Equilibrium; 気体輸送法; 溶解平衡

Removal of phophorus is one of the major problems on the purification of molten silicon for solar cell. The Gibbs energy change of phosphorus dissolution into molten silicon was determined in the temperature range from 1723 to 1848 K by equilibrating a molten silicon-phosphorus alloy in a controlled phosphorus partial pressue and is expressed by the following equations.1/(P_2(g)=P__-(mass pct, in Si)DELTAGﾟ=-139,000((]SY.+-。[)2,000)+43.4((]SY.+-。[)10.1T)(J/mol)Possibility of removing phosphorus from silicon melts by vacuum treatment and the accompanying yield of silicon during the refining process are discussed.Titanium and iron in silicon are known as harmful "life time killer" impurities which shorten the life time of excited carriers in silicon solar cell and disturb power generation. Therefore, the removal of titanium and iron is one of the most important topics for the production of solar grade silicon.Thermodynamic properties of titanium and iron in molten silicon were determined at 1723K by equilibrating molten silicon-titanium alloys or molten silicon-iron alloys with molten lead, which has a limited mutual solubility for both alloys. The activity coefficients of infinite dilution, self-interaction coefficients of titanium and iron in molten silicon, and the Gibbs energy change of mixing for silicon-titanium and silicon-iron at 1723K relative to pure liquid silicon, titanium, and iron, were determined.

磷的去除是太阳能电池用熔融硅净化的主要问题之一。在1723-1848K的温度范围内，通过控制磷分压使熔融的硅-磷合金平衡，测定了熔融硅中磷溶解的吉布斯能量变化，其表达式为1/(P_2(G)=P_-(质量百分数，在硅中)DELTAGﾟ=-139,000(()SY·+-)。[)2,000)+43.4((]正数+-。讨论了真空处理硅熔体中磷的可能性和精炼过程中硅的产率。硅中的钛和铁被认为是有害的“寿命杀手”杂质，它缩短了硅太阳能电池中激发载流子的寿命，干扰了发电。因此，钛和铁的脱除是生产太阳能级硅的重要课题之一。在1723K下，钛和铁在硅液中的热力学性质是通过平衡熔融的硅-钛合金或熔融的硅铁合金和熔融的铅来测定的，这两种合金的相互溶解度有限。测定了1723K时钛和铁在硅液中的无限稀释活度系数、自作用系数以及硅-钛和硅-铁在1723K时相对于纯液态硅、钛和铁的混合吉布斯能量变化。