| AVS 62nd International Symposium & Exhibition | |
| Nanometer-scale Science and Technology | Tuesday Sessions |
| Session NS+EN+SS-TuA |
| Session: | Nanophotonics, Plasmonics, and Energy |
| Presenter: | Carlo Mennucci, Department of Physics, University of Genova, Genova, Italy |
| Authors: | C. Mennucci, Department of Physics, University of Genova, Genova, Italy C. Martella, University of Genova, Italy M.C. Giordano, University of Genova, Italy D. Repetto, University of Genova, Italy F. Buatier de Mongeot, University of Genova, Italy |
| Correspondent: | Click to Email |
Here we report on self-organised nanofabrication method applied to substrates of relevance in the field of optoelectronic and photonics in view of light trapping applications. We demonstrate the optical functionalization of glass [1], crystalline semiconductor (GaAS and Si [2]) and TCO substrates recurring to a self-organised pattern formation based on low-energy Ion Beam Sputtering (IBS). High aspect ratio nanoscale features are formed recurring to defocused IBS through a self-organised sacrificial Au nanowire stencil mask. Ion-beam irradiation at grazing angle leads to the formation of quasi-periodic one-dimensional nanostructures with a characteristic lateral size in the range of 200nm and a root-mean-square roughness (σ) of the surface, measured by Atomic Force Microscope, ranging from 80 to 150nm.
These nanostructures confer broadband anti-reflective bio-mimetic functionality to crystalline semiconductor substrates (GaAs and Si [2]) as well as to glass and TCO substrates in the Visible and Near Infra-Red part of the spectrum. In fact, suppression of the reflected light intensity is due to high aspect ratio sub-wavelength features which leads to a progressive transition of the refractive index from the value of air to that of the substrate (index grading) analogous to that observed in the corneas of nocturnal moths. At the same time the patterned substrates have shown enhanced broadband light scattering due to the extended vertical dynamic of the surface corrugations with lateral size comparable or bigger than light wavelength. Moreover, Angular Resolved Scattering measurements has recently proved that nanostructured glasses can scatter light in the Visible and Near Infra-Red range of spectrum more efficiently and at wider angles with respect to standard Ashai-U substrates commonly used in optoelectronic device applications.
In order to asses the light trapping effect, identical amorphous thin film silicon solar cells (p–i–n single junctions) are grown on nano-patterned and on reference flat glass superstrates.Their performance is assessed by measuring their I–V characteristic and EQE under standard AM1.5g test conditions. The first encouraging results demonstrated that solar cells grown on patterned substrates with RMS roughness σ around 80 nm exhibit a 15% relative enhancement in photocurrent.
References:
[1] C. Martella, D. Chiappe, P. Delli Veneri, L.V. Mercaldo, I. Usatii, F.Buatier de Mongeot, Nanotechnology 24 (22), 225201 (2013).
[2] C. Martella, D. Chiappe, C. Mennucci, F. Buatier de Mongeot ,J.Appl.Phys. 115,194308 (2014).