Clean Synthesis and Formation Mechanisms of High‐Purity Silicon for Solar Cells by the Carbothermic Reduction of SiC with SiO2. Issue 14 (10th April 2019)

• Record Type: Journal Article
• Authors: Liu, Yang; Wang, Shuai; Jiang, Shengnan; Kong, Jian; Wang, Xiaofeng; Gao, Bo; Xing, Pengfei; Luo, Xuetao
• Is Part Of: ChemistrySelect. Volume 4:Issue 14(2019)
• Page Start: 4025
• Page End: 4034
• Publication Date: 2019-04-10
• Subjects: Synthesis -- Formation mechanisms -- In-situ silicon -- Solar cells -- Catalyst of Fe2O3 -- Carbothermic reduction; Chemistry -- Periodicals; 540.5
• DOI: 10.1002/slct.201900287
• Languages: English
• ISSNs: 2365-6549

Abstract

Abstract: Metallurgical synthesis of solar grade silicon (SoG−Si) is an existing challenge due to the strict chemical composition of silicon for solar cells. Here, we report a green and facile approach to synthesize high‐purity silicon (99.98 wt%, 0.12 ppmw B and 0.18 ppmw P) for solar cells by the carbothermic reduction of SiC with SiO2 in a vacuum graphite resistance furnace. Catalyst of Fe2 O3 plays the role of reducing the concentration of CO(g), lowering the energy consumption and improving the purity and yield of silicon. The present work is one‐step to obtain silicon with less B and P, but it is composed of silicon synthesis, oxidation refining, vacuum refining and blowing refining, which discloses an innovative chemical concepts of in‐situ synthesis combined with refining. According to the characterizations of the reacted SiC particles performed by XRD, Raman, PL, XPS, SEM and TEM, the morphologies and formation mechanisms of the in‐situ silicon from the horizons of atomic scale were revealed for the first time. It was evidenced conclusively that the Si−C bonding is broken from the (006) planes of 6H‐SiC at 1850°C by the reaction of SiC(s) + 2SiO2(l) =3SiO(g) + CO(g), and then the silicon nucleates on the (101) planes of 6H‐SiC and grows along the [111] direction at 1950°C via the vapor‐solid reaction of SiO(g) + SiC(s) =2Si(l) + CO(g) . Abstract : High‐purity silicon for solar cells was first synthesized by the chemical reaction of SiC with SiO2 . Formation mechanism of in‐situ silicon from atomic scale is the first delivered, and it is evidenced conclusively that the silicon is fabricated via the reaction of SiO(g) + SiC(s) = 2Si(l) + CO(g) .