. . . . . . . . . .    ANM 2010     3rd International Conference on Advanced Nano Materials     12-15 September 2010 - Agadir, Morocco Back    Abstract ANMM283 20 NM THICK INCUBATION-FREE P-TYPE NANOCRYSTALLINE SILICON THIN FILMS GROWN IN PRESENCE OF TRIMETHYLBORON BY RF-PECVD TECHNIQUE FOR SOLAR CELL APPLICATIONS S.A. Filonovich, H. Águas, A. Vicente, A. Araujo, I. Bernacka-Wojcik, M. Vilarigues, E. Fortunato, R. Martins CENIMAT/I3N, Departamento de Ciência dos Materiais, FCT-UNL, 2829-516 Caparica, Portugal Departamento de Conservação e Restauro, FCT-UNL, 2829-516 Caparica, Portugal . In this work we investigate the influence of deposition parameters on the optical, structural and electronic properties of p-type nanocrystalline Si (nc-Si:H) thin films using trimethylboron (TMB) as a dopant gas. The obtained films were characterized by Spectroscopic Ellipsometry, Raman Spectroscopy, electrical conductivity measurements and applied in amorphous and nanocrystalline solar cells (SCs) as a window layer. Using relatively high gas pressure (3 Torr), high hydrogen dilution (98%) and low deposition temperature (150ºC) we achieved dark conductivity, σd, values of 9 S/cm for a thin film with the thickness of 200 nm. Modelling of spectroscopic ellipsometry data indicates that the growth of nanocrystalline films occurs by a sub-surface incubation layer mechanism, instead of the typical incubation layer at the interface substrate – film. Special attention was paid to deposition of very thin (~20 nm) p-type nc-Si:H films. The σd value remains high, i.e. more than 1 S/cm, in a wide range of the film thicknesses – from 27 to 212 nm. However, a decrease in thickness from 27 to 22 nm, leads to a drop of σd more than two orders of magnitude. In this work we also investigate the origin of such behavior, and propose a way for improvement of the electronic properties by exposure of the film’s surface to the hydrogen plasma. Application of short term (3 minutes) hydrogen plasma treatment modifies both surface and sub-surface layers, and leads to an increase of the σd up to 10 times. However, longer hydrogen plasma treatment can be detrimental. P-type nc-Si:H layers were used as a window layers in amorphous and nanocrystalline SCs, and preliminary results of non-optimized SCs exhibit low series resistance and efficiency about 6%. A further improvement of the SC operation is expected upon optimization of the SC configuration, e.g. inclusion of buffer layer, light trapping techniques, etc. . © nanoAC . . . . . . . . . .

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