The wireless energy transmission technologies are gaining more and more popularity. Today they are used for wire-free charging of smartphones, and in future they may become instrumental for electricity transmission with the help of lasers: one laser will be sending a beam to the photo-voltaic converters of the other laser, they will be capturing the rays and convert them into electricity. However, to scale this technology the converters need to be as small as possible.
To achieve this, scientists from Physics and Engineering Institute of RAS developed a photo-voltaic converter based on gallium arsenide — a compound of gallium and arsenic. The structure in the form of trapezoidal layer 45 µm (comparable to a hair diameter) made of aluminium, gallium and arsenic alloy transmitted laser emission. Due to the fact that the aluminium content in the alloy varied depending on the specific section of the layer, the light at the ends of the wave duct was refracted differently. This allowed for changing the trajectory of the laser beam with 0.85 µm wave-length (the infra-red spectrum). During the pilot testing in the lab, the beam was focused on the photo-active part of the converter made of gallium arsenide with the electronic and hole conductivity zones. The light particles when hitting this material turned into charge carriers, hence, into electric current.
To understand the smallest possible size of this converter (without compromising its efficiency), the authors designed the devices of various length – from 80 to 750 µm (0.08–0.75 mm). It turned out that given the converter length from 0.2 to 0.75 mm its efficiency factor was about 45%, while given the length of 0.08 mm it was reduced down to 30%. Such difference was associated with the fact that part of laser beams were not sufficiently refracted while passing through the wave duct and did not hit the photo-responsive element.
“Even though some foreign researchers report about the converters with 70% efficiency factor, their manufacturing is much more labour-intensive, and the power density of the falling laser emission converted by them does not exceed 30 W per one square centimetre. Our technology is simpler and 10% more efficient versus the existing silicon-based analogues, the power density of the falling laser emission converted by our devices reaches 10 KW per one square centimeter”, the Russian Science Foundation is citing Vladimir Khvostikov, the lead research fellow of photo-voltaic converters laboratory of Physics and Engineering Institute of RAS.
