Innovative technology for silicon low cost production for photovoltaic use

Kurzfassung

A new Italian SME working in photovoltaic field proposes a new technique for the silicon production. This method, using a Plasmatron system, favours production of the raw material at lower cost and with reduced impurity levels while necessitating a lower quantity of energy. The technology is in the development phase, and the first experiments have been done. The company are looking for industrial partners, venture capitalists and technological partners to enter the next project phase.

Details

The use of silicon in semiconductor devices demands much greater purity than afforded by metallurgical-grade silicon. Actually the Siemens process is used to produce polysilicon with the impurity levels requested, but it is an expensive process.
The high costs of polysilicon production contribute to making the photovoltaic KWh less competitive than the conventional KWh.
There is a need to develop a lower-cost silicon production process.
An Italian SME is developing a new, less expensive method for silicon production. This innovative method uses a Plasmatron system to produce poly-silicon.
The Plasmatron system proposed uses a free-space reactor so that the silicon can circulate unhindered in a free space.
A gaseous precursor is introduced into a Plasmatron, where it receives sufficient thermal energy to separate the silicon from its by-products. The silicon falls by force of gravity and is collected. The by-products in gaseous form are expelled from the chamber and recycled.
Product/system/innovative process:
- Substitution of the Siemens process with a Plasmatron reactor.
- Use of a system without seeds.
- Use of all Chlorosilane as precursor.
- On-site compacting of silicon powder.

Innovative Aspects:
- Avoids heat dispersion and allows reduction of costs.
- High speed of deposition, efficiency of conversion and low amount of electrical energy necessary for the production of silicon.
- Avoids the possibility of silicon oxidising.

The process takes advantage of the entire available chamber space: the speed of deposition is greatly increased. In addition, the precursors conversion efficiency is much improved.
It therefore emerges that recycling is necessary, essentially, for hydrogen alone.
All these advantages can be translated into the low quantity of electric energy needed to produce one kg of silicon.
In theory it is possible to obtain 1 kg of silicon powder with only 30 KWh of electric energy: approximately half the electrical energy consumed in the Siemens process.
The first experimental results have been positive and encouraging.