A sensor that turns light into an electrical signal at an astounding 200 percent efficiency has been created by scientists.
This figure, which appears to be impossible, was discovered using the peculiarities of quantum physics.
The team behind the invention says that because of the photodiode’s sensitivity, it may be utilized in technology that monitors a person’s vital signs (such as heartbeat or breathing rate) without anything having to be introduced into or even attached to the body.
The quantity of light particles that can be converted into electrical signals by a photodiode is often used to determine its efficiency.
Here, scientists are discussing a topic that is similar to but slightly more specific: photoelectron yield, or the number of electrons produced as a result of photons striking the sensor.
Rather than the amount of electrical power generated, a photodiode’s quantum efficiency—the fundamental ability of a material to produce charge-carrying particles at a fundamental level—determines the photoelectron yield.
Rene Janssen, a chemical engineer from the Eindhoven University of Technology in the Netherlands, says, “[T]his sounds incredible, but, we’re not talking about normal energy efficiency here,”
“What counts in the world of photodiodes is quantum efficiency. Instead of the total amount of solar energy, it counts the number of photons that the diode converts into electrons.”
The group’s initial project involved a system that merged perovskite and organic solar panel cells.
The researchers were able to reach a 70 percent quantum efficiency by stacking the cells so that light missed by one layer is captured by another.
A more green light was added in order to raise this number. The sensor was additionally enhanced to enhance its capacity to filter various forms of light and react to absolutely no light.
This increased the photodiode’s quantum efficiency past 200 percent, though it is currently unclear why this improvement is taking place.
The method by which photodiodes generate a current may be crucial. Electrons in the photodiode material are excited by photons, which causes them to move and accumulate charge.
According to the researchers’ theory, the green light might potentially release electrons on one layer, which would only become current when photons hit a different layer.
Chemical engineer Riccardo Ollearo from the Eindhoven University of Technology believes that the additional green light causes an accumulation of electrons in the perovskite layer.
When infrared photons are taken in by the organic layer and absorbed, this functions as a reservoir of charges that are released.
As said, “In other words, every infrared photon that gets through and is converted into an electron, gets company from a bonus electron, leading to an efficiency of 200 per cent or more.”
A more sensitive photodiode is one that is better able to detect extremely slight changes in light at a greater distance; it is also more effective.
This brings us full round to the measurement of breathing and heartbeat rates.
The researchers recorded minute variations in the infrared light reflected back off a finger at a 130-centimeter distance using their incredibly thin photodiode, which is one hundred times thinner than a sheet of newspaper (51.2 inches).
This was demonstrated to match blood pressure and heart rate, very similarly to a smartwatch sensor but working across a table.
The scientists measured respiration rates from small chest motions using a similar setup.
If the technology is effectively developed, it has the potential to be used for a variety of monitoring and medical applications.
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