{"id":117624,"date":"2026-09-24T11:40:32","date_gmt":"2026-09-24T09:40:32","guid":{"rendered":"https:\/\/www.sonnenseite.com\/?p=117624"},"modified":"2026-09-24T11:40:34","modified_gmt":"2026-09-24T09:40:34","slug":"harvesting-hot-electrons-could-break-solar-panel-barrier","status":"publish","type":"post","link":"https:\/\/www.sonnenseite.com\/en\/science\/harvesting-hot-electrons-could-break-solar-panel-barrier\/","title":{"rendered":"Harvesting hot electrons could break solar panel barrier"},"content":{"rendered":"\n

Physics predicts that no more than 33 percent of the solar energy that falls on a solar panel can be converted into electricity. However, experimexents and simulations by scientists at the University of Groningen (the Netherlands) revealed a way to harvest extra energy from \u2018hot electrons\u2019, which could break this barrier.<\/p>\n\n\n

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Reabsorption of lost heat (hot phonon bottleneck) and occupied energy levels (Band filling) slow the loss of energy from hot electrons. | Image ACS Energy Letters<\/figcaption><\/figure>\n<\/div>\n\n\n

When light falls on a solar panel, the energy of the photons brings electrons in the solar cell material into an excited state, thus transferring the energy to them. This reaction can free an electron from the solar cell material and create a voltage.<\/p>\n\n\n\n

However, very energetic photons give the electrons extra energy, producing \u2018hot electrons\u2019. In theory, the extra energy these hot electrons carry could increase the voltage. In practice, the extra energy is lost as heat in a matter of picoseconds (0,000000000001 second). \u2018This means that the energy is lost before the hot electron exits the solar cell material\u2019, says Jan Anton Koster, Professor of Physics of Novel Semiconductors and Devices at the University of Groningen.<\/p>\n\n\n\n

Scepticism about the claims<\/h4>\n\n\n\n

However, in an experimental setup, his colleague Maria Antonietta Loi, professor of Photophysics and Optoelectronics, managed to produce a delay in heat loss by hot electrons. She created a solar cell material called tin-based perovskite, and observed that the loss of extra energy is slowed down to nanoseconds, roughly a factor of 1,000. \u2018The measurements were clear, but we didn\u2019t understand the physics behind this\u2019, says Koster. This led others in the field to question this claim. \u2018We even started to doubt the measurements ourselves\u2019, he admits.<\/p>\n\n\n\n

In order to solve this conundrum, Koster and his PhD student Tim Faber used simulations to study the physics of this energy loss. They found that in perovskite solar cells, two different mechanisms combine to extend the time it takes hot electrons to lose the extra energy.<\/p>\n\n\n\n

Nanosecond range<\/h4>\n\n\n\n

When energy is lost as heat, the environment surrounding the electrons will become warmer. Koster and Faber realised that this lingering heat can be reabsorbed by the electrons. \u2018When we added this well-known process called Hot Phonon Bottleneck to the simulations, it slowed the loss of energy, but not enough to explain our measurements.\u2019 This required adding a second mechanism to the simulation.<\/p>\n\n\n\n

The extra energy of hot electrons can bring them into a number of excited states. Energy loss means that the excited state is reduced to a lower energy level in discrete steps. However, when the different steps in this process are already occupied, the way down to the lowest energy level is more difficult and takes more time. This is called the Burstein-Moss effect. Koster: \u2018When we added this process to the simulation as well, we saw that energy loss was now in the nanosecond range, as seen in the experiments by Maria Loi.\u2019<\/p>\n\n\n\n

As both of these processes are present in tin-based perovskite solar cells, Koster and his team finally understood why the energy loss of hot electrons was slowed down. There are many other questions that still need answers, but in theory, this discovery could allow the creation of more efficient solar cells, beyond the theoretical limit of 33 percent.<\/p>\n\n\n\n