A Si-rich Si<inf>x</inf>C<inf>1-x</inf> based p-n junction photovoltaic solar cells

A Si-rich silicon carbide (Si1-xCx) based p-n junction photovoltaic solar cells is demonstrated by growing the non-stoichiometric SixC1-x film with plasmas enhanced chemical vapor deposition (PECVD) at low RF plasmas powers. By decreasing RF plasma power from 100 to 20 W at medium substrate temperature of 500°C, the X-ray photoelectron spectroscopy (XPS) analysis confirms an decreasing composition ratio of carbon induces a linear increasing fraction index x of SixC1-x from 0.63 to 0.66. The optical bandgap is concurrently reduced from 2.05 to 1.49 eV, corresponding to a change of cut-off wavelength from 770 to 600 nm after fitting by Tauc's equation. At RF plasmas power of 20 W, the broadband absorption spectrum at visible region (400-600nm) shows highest optical absorption coefficient of up to 1.3×105 cm-1 which is comparable with the crysatalline Si. The ITO(80nm)/P-SiC/i-SiC/n-SiC/Al(200nm) solar cell provides a conversion efficiency increasing from 7×10-3 to 0.37 % by thinning the n-type SiC thickness. After decreasing its series resistance from 10 to 0.6 Ω, the conversion efficiency is significantly enhanced up to 3%. © 2012 IEEE.