International. In Neuchâtel (Switzerland), researchers from the Cheops project have combined solar cells based on silicon and perovskite. The resulting efficiency of 25.2% is a record for this type of tandem cell. Their innovative yet simple manufacturing technique could be integrated directly into existing production lines, and efficiency could eventually rise above 30%.
In the field of photovoltaic technologies, silicon-based solar cells account for 90% of the market. In terms of cost, stability and efficiency (20-22% for a typical solar cell on the market), they are far ahead of the competition.
However, after decades of research and investment, silicon-based solar cells are now close to their theoretical maximum efficiency. As a result, new concepts are required to achieve a long-term reduction in solar electricity prices and allow photovoltaic technology to become a more widely adopted way of generating power.
One solution is to place two different types of solar cells on top of each other to maximize the conversion of light rays into electrical energy. These "double-bonded" cells are being extensively researched in the scientific community, but they are expensive to make.
Now the research teams in Neuchâtel, from the EPFL Photovoltaic Laboratory and the CSEM photovoltaic center, have developed an economically competitive solution. They have integrated a perovskite cell directly on top of a standard silicon-based cell, obtaining a record efficiency of 25.2%. Their production method is promising, as it would add only a few additional steps to the current silicon cell production process, and the cost would be reasonable. His research has been published in Nature Materials.
Perovskite's unique properties have led to a great deal of research on its use in solar cells in recent years. In the space of nine years, the efficiency of these cells has increased by a factor of six. Perovskite makes it possible to achieve high conversion efficiency at a potentially limited production cost.
In tandem cells, perovskite complements silicon: it converts blue and green light more efficiently, while silicon is better at converting red light and infrared light. "By combining the two materials, we can maximize the use of the solar spectrum and increase the amount of energy generated. The calculations and the work we have done show that an efficacy of 30% would soon be possible," say the study's lead authors, Florent Sahli and Jérémie Werner.
The new type of tandem cell is highly efficient and directly compatible with monocrystalline silicon-based technologies, which benefit from long-standing industrial expertise and are already being produced cost-effectively. "We are proposing to use equipment that is already in use, simply by adding some specific stages. Manufacturers will not adopt a completely new solar technology, but will simply upgrade the production lines they are already using for silicon-based cells," explains Christophe Ballif, head of EPFL's PHOTOVOLTAIC Laboratory and CSEM's PHOTOVOLTAIC center.
At the moment, research continues to further increase efficiency and give perovskite film greater long-term stability. Although the team has made a breakthrough, there is still work to be done so that its technology can be adopted commercially.
Source: Cheops.
