Researchers from Aalto’s (University of Aalto) university, Finland, established a new record by efficiency of transformation of a sunlight to electric energy for silicon solar batteries. So-called black silicon became a key to this achievement which for the whole four percent exceeded the previous record indicator, and solar batteries on the basis of such silicon are capable to collect effectively light falling on their surface under big corners.
Black silicon turns out from usual silicon on which surface dense “wood” from nanodimensional silicon needles is grown up. Such transformation of a surface does material to less reflecting due to formation of the optical traps catching light photons falling under a big corner to the surface plane. Such type of solar batteries is ideal the decision for obtaining energy in the areas which are located at big heights, besides, such solar batteries will be cheaper in comparison with usual as they do not need drawing a special antiglare covering.
The main problem which interferes with distribution of solar batteries from black silicon so far, is a so-called recombination of carriers of electric charge. When the photon of light faces atom of silicon, energy of a photon releases an electron of which, as we know, electric current is formed. Rather often this electron again unites with the empty place, an electronic hole, and energy of a photon of light is wasted, turning in nobody the necessary heat. The quantity of such recombinations in direct ratio of the area of silicon, and in the black silicon possessing the big area, amount of the lost energy makes about a half.
The increase in an indicator of efficiency to 22.1 percent became possible thanks to the thin aluminum film covering a surface of nanodimensional structures which acted as chemical and electronic protection, interfering with a recombination of carriers of electric charge. Besides, in the new solar battery additional metal conductors which improved branch of free electrons, i.e. the developed energy battery on its reverse side were used.
Two methods used by researchers allowed to keep from a recombination only four percent from the developed energy. Nevertheless, the potential of this technology is still not settled. In the near future scientists will make solar batteries on the basis of black silicon of n-type, but not p-type in which still some new decisions and materials will be used that will allow to increase their efficiency by some size.