Optimization of the Granulation Binders of High-Purity Carbothermic Reduction for Solar-Grade Silicon

Abstract

The direct carbothermic reduction process from high-purity silica is promising for next-generation low-cost silicon solar cells. In this process, the granulation process is essential to avoid blowout of the silica powder. In this study, we investigated the effect of binders on this reduction process using four kinds of binders. The real-time monitoring of the chamber pressure and quadrupole mass spectroscopic analysis indicated the sign of the blowout phenomena of the generated CO gas and decomposition gas of the binders. In the case of starch and sucrose, the strengths of granules were not enough to the process with the pressure of the generated CO gas, while the granules with enough strength, namely, the ones with polyvinyl alcohol (PVA) and carboxymethyl cellulose (CMC), resulted in silicon yield of 33.8% and 27.8%, respectively.

Effect of pellet size and additive on silica carbothermic reduction in microwave furnace for solar grade silicon

“…In addition, a new method was used for weight loss of SiO and CO gases [3]. As the chemical reaction in equation 4 shows, the silicon carbide can enhance the silicon production yield [1], and it can prevent the loss of SiO gas as shown in the reaction equation 5. In turn, silicon monoxide (SiO) is an important element to increase the amount of silicon.…”

“…For more than 100 years, the process of silicon production has been in continuous development for application in electronic chips and solar panels. Several research projects have been conducted to produce low cost silicon for the photovoltaic industry [1].…”

Ultrafast carbothermal reduction of silica to silicon using a CO2 laser beam

“…It requires considerable time and energy to produce pure silicon from silica by reduction because of the high bonding energy between silicon and oxygen atoms 1 . In industry, carbothermal reduction using an electric arc furnace is adopted to produce pure silicon from silica because this system is considered to be the most economical route in large-scale production 2 – 4 . Carbothermal reduction using an arc furnace has been thoroughly investigated to date 5 – 8 ; however, the traditional carbothermal reduction process requires large-scale facilities to achieve high thermal efficiency during the high-temperature process and requires a stabilization process for normal operation after process initiation 3 .…”