Solar cell hits record efficiency

Sanyo this week unveiled a new solar cell that boasts a world-leading efficiency of 21.1 per cent.

The release of the improved HIT (hetero-junction with intrinsic thin-layer) solar cell comes at a time when the UK is seeing a rapid increase in demand for solar power in the UK, thanks to the introduction of the feed-in tariff this past April. The ever-increasing demand for higher-efficiency solar cells is fueling a highly competitive market among photovoltaics manufacturers.

Sanyo’s newest solar cell offers a marked improvement on its previous HIT cell, which had an efficiency of 19.5%.

Sanyo achieved the increased efficiency through a new thinner tab design, increasing the area which sunlight can impinge on and using three tabs instead of two, thus reducing electrical losses. The anti-reflective coating has also been improved, reducing the amount of sunlight reflected, especially when the sun is at a low position.

The HIT cell structure is based on sandwiching a mono-crystalline silicon wafer between two amorphous silicon layers to help absorb a wider range of the solar spectrum. The amorphous silicon also has a positive temperature coefficient, meaning the solar cell efficiency does not decrease as much with a rise in temperature as it does in purely mono-crystalline cells.

The actual module efficiency is 18.6 per cent, which is at the top end of module efficiencies for silicon solar modules. Sanyo will produce them at its factory in Hungary, and also aims to increase production capacity from 165MW to 315MW by March 2011.

With every percentile increase in efficiency, a solar cell’s potential savings — and earnings — increases substantially due to the long life-span, typically at least 20 years, of photovoltaics. The higher efficiency means the area used on roofs for solar panels can be more effectively used and, thus, a greater income can be generated from the feed-in tariff.