The Chinese company LONGi has broken the efficiency record for a photovoltaic cell with a resounding 33.9%. Manufacturing with perovskites, the holy grail of solar technology, continues to bring joy to the industry, which by combining them with silicon, has managed to overcome for the first time the theoretical limit of conventional single-junction cells.

World record efficiency. Crystalline silicon and perovskite photovoltaic cells have reached 33.9% efficiency or capacity to convert sunlight into electricity. The "miracle material" has come a long way since, in 2009, the first cell made with perovskites achieved an efficiency of 3.8%.

The last two years have been particularly exciting for the sector. Researchers at Helmholtz-Zentrum in Berlin were the first to approach 30% efficiency with silicon-perovskite tandem cells at the end of 2021. In the summer of 2022, the EPFL school in Lausanne, Switzerland, surpassed them with 31. 3%. HZB regained the record in April 2023 with 32.5%, but the KAUST photovoltaic laboratory in Saudi Arabia took it away the following month.

China has made the entire world dependent on its solar technology. In three years, 80% of the industry will leave its factories.

Overcoming the theoretical limit of commercial cells. The new record of 33.9% from the Chinese company LONGi is not far from the previous one. 33.7% had achieved KAUST university in May 2023. However, LONGi's record is a very special milestone for silicon and perovskite cells because it leaves behind the theoretical limit of single junction solar cells, which are the most used.

It is known as the Shockley-Queisser limit and was set in 1961 at 33.7%. It was calculated by imagining a cell with a bandgap of 1.34 eV, optimal for the spectral distribution of sunlight. Over the years, single-junction crystalline silicon panels have approached this limit, which has eventually been surpassed by other materials. The theoretical efficiency limit of crystalline silicon and perovskite tandem cells is 43%.

The silicon-perovskite tandem. Perovskites are a family of synthetic materials similar to the mineral of the same name, which has a crystalline structure. Semiconductor cells or films made of crystalline silicon and perovskite are attractive for their ability to absorb light, but also for their flexibility, ease of manufacturing and price.

Instead, its durability has traditionally been the main cause of concern. The first perovskite cells, developed between 2009 and 2012, lasted just a few minutes. They now take thousands of hours to degrade, but their durability and reliability are still below that of more conventional cells.

A promising future. Perovskites can be "tuned" to absorb light in the visible and near-infrared spectrum, so these tandem cells can produce electricity more consistently throughout the day and in different weather conditions. There are those who are even considering converting our windows into solar panels thanks to this material, but the commercial phase of its development has yet to take off.

It won't take long to see it. British startup Oxford PV, spun out of Oxford University, is already in the process of commercializing the technology, and plans to begin full-scale production at a German plant later this year. Silicon solar panels have reached their physical limits, but solar energy has a promising future with perovskites.