For years, one of the most promising emerging solar technologies has been what is called "black silicon" solar cells. The technology is really a solar cell composed of nano-sized needles atop a silicon wafer that has been proven to capture more of the light spectrum and harness energy from even low light angles.
Gains have been made in the efficiency of black silicon solar cells, but they have remained confined to the lab. That may all change soon. Researchers at Aalto University have produced black silicon solar cells capable of reaching a 22.1 percent conversion efficiency, which is a full 4 percent increase from the previous record.
This gain was achieved by applying a thin aluminum film on the nano-structures and by integrating all metal contacts on the back side of the cell. This bump in efficiency now puts black silicon in the same efficiency range as conventional crystalline silicon solar cells, which means we could start seeing this technology in the real world soon.
Aalto University sees another major benefit from having this technology in the marketplace. The university reports, "The energy conversion efficiency is not the only parameter that we should look at explains Professor Hele Savin from Aalto University, who coordinated the study. Due to the ability of black cells to capture solar radiation from low angles, they generate more electricity already over the duration of one day as compared to the traditional cells.
This is an advantage particularly in the north, where the sun shines from a low angle for a large part of the year. We have demonstrated that in winter Helsinki, black cells generate considerably more electricity than traditional cells even though both cells have identical efficiency values."
The main reason that the black silicon performs so well is that the nano-structures make the cells far less reflective, which allow them to absorb more light. Researchers think that the cells could be cheaper to manufacture than conventional cells because they wouldn't require the anti-reflective coatings that current solar cells do.
The next step for the researchers is to further develop the technology with support from the European Union. They will apply their technology to other cell structures like thin and multi-crystalline cells and also test them in devices like screens and photodetectors.