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The possibility of manufacturing high-performance thin solar cells

 

Scientists from the California Institute of Technology (USA) showed how to increase the proportion of radiation absorbed by the thin solar cells.
The aim of research was to overcome the classical limit the effectiveness of the “capture” of radiation, which in 1982 established the Elie Yablonovich considering homogeneous bulk semiconductors. His theory is valid in the case of simple light “traps” that are described from the standpoint of geometrical optics and built on the effect of total internal reflection at the interface between the semiconductor (such as silicon with a refractive index n = 3,5) and the environment – air. In order to increase the path length of the radiation in the material, to maximize absorption and approach the fundamental limit, the interface in such schemes textured.
However, our calculations inapplicable to modern solar cells, which may have heterogeneous structure and thickness, is much inferior to the radiation wavelength. Here, as shown by the author of the new work, the traditional limit can be overcome by increasing the local density of photon states in the absorbing area of ​​the device.

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Americans have also analyzed different ways to increase the density of states, finding that the desired effect can be achieved with metal coatings, photonic crystals, placed above or below the active layer or plasmonic elements. The last option is analyzed in the figure above, which shows the results for the organic absorbing layer P3HT: PCBM thickness of 10 nm, covered by periodic arrays of silver resonators. Red, orange and blue denotes the fraction of radiation absorbed by the use of arrays with different parameters, gray – indicators of “pure» P3HT: PCBM, black – Yablonovich`s limit.

Predict when these technologies will be applied in practice, it is difficult: the modification of the structure of the solar cell, of course, complicates the process of its production, and with it grows and its cost.