The mystery of the energy needed – solved

The efficiency of solar cells can be increased by taking advantage of a phenomenon called single cooling. However, unexplained energy loss during the reaction has been a major problem so far. A research group led by scientists at Linköping University, Sweden, has found out what happens during single cooling and where the lost energy is going. The results were published in the journal Physical Science cell reports.

Solar energy is one of the most important fossil-free and eco-friendly sources of electricity. The silicon-based solar cells currently in use can use about 33% of the energy in sunlight and convert it into electricity. This is because the light packets, or photons, have energy in the sun’s behavior that is too low to be captured by the solar cell, or too high, so that part of the energy is dissipated for heat dissipation. This highest theoretical efficiency is called the Shockley-Queisser boundary. In practice, the efficiency of modern solar cells is 20-25%.

However, a phenomenon in molecular photophysics called singlet fission can allow photons with higher energy to be utilized and converted to electricity without heat loss. In the last few years, single uniforms have attracted more attention from scientists, and intense activity is underway to develop the best material. However, so far it is difficult to design a material like this through invisible energy loss during single cooling. Researchers were unable to agree on the origin of these energy losses.

Now, researchers at Linköping University, along with colleagues in Cambridge, Oxford, Donostia and Barcelona, ​​have discovered where the energy goes during single cooling.

“Singlet cooling takes place in less than a nanosecond, which makes it very difficult to measure. Our detection allows us to open the black box and see where the energy is going through the reaction. In this way, we will be able to make the best material to increase the efficiency of solar cells, “said Yuttapoom Puttisong, senior lecturer in the Department of Physics, Chemistry and Biology at Linköping University.

Part of the energy disappears in the form of a clear intermediate state, and this is a problem that needs to be solved to achieve efficient single cooling. Finding out where energy is going is a big step on the path to much higher solar cell efficiency – from the average 33% to over 40%.

The researchers used a modified magnetic magneto-optical transduction method to identify energy loss conditions. This method has particular advantages in that it can analyze the ‘fingerprints’ of the single scattering reaction at a nanosecond timeframe. A monoclinic crystal of polyene, diphenyl hexatriene (DPH), was used in this study. However, this new method can be used to study single cooling in a wider material library. Yuqing Huang was previously a doctoral student in the Department of Physics, Chemistry and Biology at Linköping University, and the first author of the article now published in a newly established journal, Physical Science cell reports:

“The single scattering process takes place in the crystalline material. If we can maximize this material to retain as much energy as possible from the single scattering, we will be much closer to it in use. In addition, the single – release material will contain a processing solution, which makes it cheap to manufacture and suitable for integration with existing solar cell technology, “said Yuqing Huang.

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The research was specifically funded by the Swedish Research Council and the Knut and Alice Wallenberg Foundation.

The article: Competition between the creation of a triplet pair and an excimer-like replay will control the single-player production Yuqing Huang, Irina A. Buyanova, Chanakarn Phansa, Maria E. Sandoval-Salinas, David Casanova, William K. Myers Neil C. Greenham, Akshay Rao, Weimin M. Chen, and Yuttapoom Puttisong Physical Science cell reports 2021 doi: 10.1016 / j.xcrp.2021.100339

Footnote: A nanosecond is a billionth of a second.