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Black Silicon Photodetector Breaks the 100% External Quantum Efficiency Limit for the First Time Ever

In a surprising twist, researchers from Aalto University have recently developed a black silicon photodetector that has reached above 130% external quantum efficiency, sending the research team into a brief state of disbelief.

An external quantum efficiency of more than 100% means that one incoming photon generates more than one electron to the external circuit – a phenomenon that hasn’t been observed up until now since the presence of electrical and optical losses has reduced the number of collected electrons.

With new silicone photodectors that exceed 100% external quantum efficiency, light-detecting devices are about to get a massive boost in performance. Image: pixabay.com, free licence

The research team believes their photodetector is the first single photovoltaic device to break past the 100% external quantum efficiency threshold at UV, which could eventually lead to efficiencies beyond the Shockley-Queisser limit.

“When we saw the results, we could hardly believe our eyes. Straight away we wanted to verify the results by independent measurements,” said Professor Hele Savin, Head of the Electron Physics research group at Aalto University.

For that, the researchers turned to the German National Metrology Institute, or the Physikalisch-Technische Bundesanstalt (PTB), known for providing the most accurate and reliable measurement services in Europe. After the analysis, Head of the PTB, Dr Lutz Werner, instantly recognised the achievement to be a significant breakthrough.

While conducting further investigation into the properties of the new device, the researchers have identified that the reason behind the exceptionally high external quantum efficiency is the charge-carrier multiplication process inside silicon nanostructures that is triggered by high-energy photons.

Apart from being a theoretical curiosity, the new invention could soon be deployed to drastically improve the performance of any device that utilises light detection, such as mobiles phones, smartwatches, medical devices, and automobile components.

In fact, the University’s spin-off company Elfys Inc. has already gained a great deal of traction in biotechnology and industrial process monitoring, among other fields, and have already started manufacturing the detectors for commercial use.

A paper detailing the breakthrough device was published in the journal Physical Review Letters.


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