Reducing the cost of solar cells

A new, less expensive grade of raw material for solar cells has been developed, and the new modules are just as efficient as current solar cells.

The aim of the EU’s three-year SINTEF coordinated FoXy (Development of solar-grade silicon feedstock for crystalline wafers and cells purification and crystallisation) programme was to develop new materials that would make future solar cells at least as efficient but cheaper than current cells.

By using a special smelter and a kiln that removes traces of carbon, scientist have shortened the long production process currently used by most solar cell manufacturers, and run full scale trials of new solar modules.

“We are very proud of what we have done,” said Marisa Di Sabatino of SINTEF Material and Chemistry, “Many people before us have been working on solar energy, but our results are actually quite important,” she added.

The team started with metallic silicon containing 1% impurities – not good enough for use in solar cells – and attempted to reduce impurities in the silicon, and the raw materials by means of heat treatment.  Silicon recycled from industry contains boron and phosphorus that can alter the electrical properties of the material, while other contaminants can lower the efficiency of the solar panels. 

The process is much less costly and energy-intensive that the conventional chemical process, and the energy used to produce them could be paid back in six months, rather than the two years it takes with today’s solar cell, explained Di Sabatino.

The scientists have also patented a new, more stable passivation process – a high temperature treatment process that protects the surface of the solar cells making them more efficient and resistant to temperature changes.

By assembling the individual cells differently – putting the n (-) and p (+) silicon vertically in the panel allowing more cells to be inserted – the team has reduced the risk of technical failure and produced a product as efficient as the current cells.  The cells are also estimated to be one Euro cheaper per Watt of electricity generated.

Although the programme has concluded, the researchers hope to continue their work by developing thinner wafers, halving the current thickness of 180-200µm.