Mar 30 2010
Thin films of silicon are attractive for use in solar cells because of their low material cost and suitability for large-scale fabrication, but their power-conversion efficiency has so far been lacking. The efficiency of thin-film-based devices, however, could rival that of bulk silicon solar cells if the surface of the thin film is engineered on the nanoscale using the specifications suggested in a theoretical study by Junshuai Li and co-workers at the Institute of Microelectronics, A*STAR, Singapore.
Trapping light with nanostructures on the surface of thin-film-based solar cells can boost the solar-to-electrical power-conversion efficiency, explains co-author Patrick (Guo-Qiang) Lo. Constructing arrays of nanopillars on the film, for instance, prolongs the path traveled by the light, allowing for more scattering and therefore increasing light absorption, he notes.
Before commencing their design, the researchers also had to consider that once absorbed, photons should efficiently generate electron–hole pairs that exist long enough to be separated in the electric field—generated in the standard p–n junction setup of solar cells—to give rise to a photocurrent. This meant that their careful and precise design involved a trade-off between the absorption of solar radiation and the efficient collection of the photo-generated carriers, which is sensitive to the detailed topographical variations of the patterned film.
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