Researchers from Aalto University have developed a Black Silicon Photodetector with a record-breaking efficiency of more than 130%.
What is Photodetector?
Photodetectors, also called photosensors, are sensors of light or other electromagnetic radiation. A photodetector has a p–n junction that converts light photons into the current. The absorbed photons make electron-hole pairs in the depletion region.
Theoretically, it was believed that the maximum external quantum efficiency of a photovoltaic device is 100% but this new photodetector has exceeded the limit for the first time.
When one incoming photon generates one electron to the external circuit, the external quantum efficiency of that device is 100%. So, an efficiency of 130% means that one incoming photon on an average generates 1.3 electrons.
“When we saw the results, we could hardly believe our eyes. Straight away we wanted to verify the results by independent measurements,” says Prof. Hele Savin, head of the Electron Physics research group at Aalto University.
The researchers at the German National Metrology Institute, Physikalisch-Technische Bundesanstalt (PTB) carried out the independent measurements
Head of the Laboratory of Detector Radiometry at PTB, Dr. Lutz Werner comments, “After seeing the results, I instantly realized that this is a significant breakthrough—and at the same time, a much-welcomed step forward for us metrologists dreaming of higher sensitivities.”
The team found out that the origin of this record-breaking external quantum efficiency is due to the charge-carrier multiplication process inside silicon nanostructures that is triggered by high-energy photons.
The phenomenon has not been observed earlier in actual devices since the presence of electrical and optical losses has reduced the number of collected electrons. But the current unique nanostructure developed at Aalto University doesn’t have recombination and reflection losses.
Photodetectors are used in a lot of devices, like cars, mobiles, smartwatches, medical devices, etc.
Now, increases efficiency directly means increased sensitivity. With this increased sensitivity, the new device is getting a lot of popularity, and Aalto University spin-off company, Elfys Inc has started producing these detectors for commercial purpose.
Garin et al. Black-silicon ultraviolet photodiodes achieve external quantum efficiency above 130%, Physical Review Letters (2020). journals.aps.org/prl/accepted/ … 234ffbcb06f4a5ba1ac5 , arxiv.org/abs/1907.13397