EU Researchers achieve breakthrough in nano-scale c-Si

European researchers have become the first successfully integrate a nanophotonic structure into a crystalline silicon solar cell, boosting its light absorption and greatly reducing silicon use. This breakthrough, the researchers say, sets a pathway for scaling down the texture of crystalline solar cells from the micro to the nano-scale.

Thinner crystalline cells could allow new applications not currently possible with c-Si technology, such as flexible solar modules or semi-transparent cells for use in solar glass and building integrated solar projects.

“We strived to enable the development of a new and disruptive solar cell generation, resulting from the marriage of crystalline silicon PV with advanced light-trapping schemes from the field of nanophotonics,” states project leader Valerie Depauw of the Belgium based Imec institute. “The main applications of our thin c-Si solar cells could be in buildings as windows and skylights, where they will bring more freedom for integration, and possibly lighter and thinner module designs.”

Adding nanophotonic structures to the surface of c-Si cells has been a major stumbling block for researchers – while the structures boost light absorption, the texturing often damages the electrical efficiency of the cell, causing major losses.

The photoNvoltaics researchers were able to create a monocrystalline cell with 8.6% efficiency at just 830nm thickness. This was achieved by combining amorphous ordered nanopatterning with an advance surface passivation. “This prompts the development of highly efficient, flexible and semitransparent photovoltaics, based on the industrially mature monocrystalline silicon technology, state the researchers in their study Sunlight-thin nanophotonic monocrystalline silicon solar cells, published in the journal Nano Futures.

The researchers used a kerfless technique to separate a micron thick film from a standard mono wafer. The researchers then used reactive ion etching to imprint a nanotexture onto surface of the cell.

Silicon costs make up the largest portion of a solar module’s overall costs, so creating thinner cells, and reducing the amount of silicon wasted in production are key areas for improvement in the eyes of manufacturers. Replacing sawing with kerfless wafer processes, and texturing surfaces to absorb more light are already recognized as two methods with the potential to further produce c-Si production costs.

The photoNvoltaics project takes this a step further, and while the cells it has produced here have not yet achieved commercially viable efficiency levels, the breakthrough could be a stepping stone towards new applications for c-Si technology, one that could see the technology applied in growing areas such as energy efficient buildings and transparent solar cells.