Light management in solar cells: Recent advances

Efficient light management is critical for the enhancement of the efficiency of solar cells. The performance of a solar cell is determined by the efficiency of the absorption process of light via excitation of electron-hole pairs and extraction of these generated charge carriers. The absorption, in turn, has a few limiting factors: one is related to the small size and acceptance angle of the active region, another to the reduced spectral sensitivity of the active material, which does not use a part of the solar radiation. Correspondingly, the energy harvesting may be improved in two ways: a) light trapping schemes may be adopted to make the cell 'thicker' by exploiting scattering and/or reflection effects. Plasmonic structures, constituted by patterned metal films or nanoparticles, demonstrated to be very effective for directing and enhancing the incident light beam. b) up- and down-conversion processes may be exploited to convert the frequencies of the solar spectrum from near-mid-IR and from blue-UV regions, respectively, to the region of maximum absorption of the cell. Thin glassy or glass-ceramic films doped with rare earth ions proved to be very suitable for this purpose. Here, an overview of recent results achieved in the use of plasmonic structures by different research groups will be reported, and different approaches will be compared.