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20% efficiency ‘realistic’ for silicon solar cells

Researchers in Germany claim to have achieved new peak efficiency for large-area easy-to-fabricate silicon solar cells.

By Isabella Kaminski

A team at the Fraunhofer Institute for Solar Energy Systems (ISE) says it has demonstrated 19.3% efficiency for a particular kind of silicon solar cell.

Researchers say that using more advanced cell structures, as compared to current industry standards, they could demonstrate that efficiencies of 20% are “realistic in the near future”.

More than 80% of the solar cells manufactured today are based on crystalline silicon. Currently, silicon solar cells convert an average of 14-19% of incidental solar energy into electricity. According to Fraunhofer ISE, researchers are already looking at the 20% efficiency mark, which could help reduce solar PV costs.

Christian Schmiga, Project Leader for high efficiency silicon solar cells at Fraunhofer ISE, says: “Just now, we were able to conclude several areas of development work on crystalline silicon solar cells. The results that we achieved belong to the best in the world.”

The investigated cell structures vary in the type of silicon material used, the base and the type of emitter (a thin layer that collects the electrical charge carriers). Solar cells with a negatively conducting base are referred to as n-type and those with a positively conducting base as p-type. The emitter always has the inverse polarisation of the base.

Schmiga says: “For processing the emitter layer, we used three different procedures as follows: aluminum alloying and boron diffusion for the p-emitter layer of our n-type solar cells and phosphorous diffusion for the n-emitter layer of our p-type solar cells.”

For an n-type silicon solar cell with an aluminium alloy emitter, researchers at Fraunhofer ISE reached a record efficiency of 19.3%. To form the emitter, they screen-printed a paste containing aluminium, followed by a short high-temperature firing step.

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