It's no secret that popular silicon solar panels are limited in how efficiently they convert light into electricity. This is because each photon knocks out only one electron, although the energy of a light particle may be enough to knock out two electrons. In a recent study, scientists at the Massachusetts Institute of Technology have shown that this fundamental limitation can be bypassed, paving the way for silicon solar cells with substantially higher efficiency.
The ability of a photon to knock out two electrons was theoretically substantiated about 50 years ago. But the first successful experiments were reproduced only 6 years ago. Then, as an experiment, a solar cell made of organic materials was used. It would be tempting to move to a more efficient and widespread silicon, which scientists have managed to master only now in the course of carrying out an enormous amount of work.
During the last managed to create a silicon solar cell, the theoretical efficiency limit of which was increased from 29,1% to 35%, and this is not the limit. Unfortunately, for this, the solar cell had to be made composite of three different materials, so in this case one monolithic silicon cannot be dispensed with. When assembled, the solar cell is a sandwich of organic material. in the form of a surface film, the thinnest (several atoms) film of hafnium oxynitride and, in fact, a silicon wafer.
The tetracene layer absorbs the high energy photon and converts its energy into two wandering excitations in the layer. These are the so-called quasiparticles. . The separation process is known as singlet exciton fission. In a rough approximation, excitons behave like electrons, and these excitations can be used to generate an electric current. The question is how to transfer these excitations to silicon and further?
A thin layer of hafnium oxynitride has become a kind of bridge between the surface tetracene film and silicon. Processes in this layer and surface effects on silicon convert excitons into electrons, and then everything goes on knurled. In the experiment, it was possible to show that in this way the efficiency of a solar cell in the blue and green spectra is increased. According to scientists, this is not the limit of increasing the efficiency of a silicon solar cell. But even for the presented technology, it will take years for its commercial implementation.
Source: 3dnews.ru