A comparative study of SiO2 deposited by PECVD and thermal method as passivation for multicrystalline silicon solar cells

This paper investigates the surface passivation effect by silicon dioxide layer formed either by a thermal oxidation process at 800 degrees C or by plasma enhanced chemical vapor deposition (PECVD) method at 400 degrees C. The passivation was applied on n(+) emitter of the p type multicrystalline silicon (mc-Si) of 1 Omega cm resistivity. The mc-Si wafers were taken from the same column of the Si cast ingot. The optical properties of thermal SiO2 and PECVD deposited SiO2. films have been investigated by ellipsometry measurements to deduce the refractive index and thickness. The reflectance spectra were measured by UV-vis-NIR spectrophotometry. For performing the antireflection (ARC) requirements in the finished solar cells. both silicon dioxide films have been covered by a TiO2 layer deposited by CVD. The mc-Si solar cells were prepared according to the technology elaborated in Photovoltaic Laboratory of IMMS. Spectral response (SR) and current-voltage (I-V) characteristics were measured and the data are correlated with optical results. The passivation effect induced by the thermal and PECVD Si dioxide layers on the solar cell parameters is discussed through the open circuit voltage and short circuit current data. (C) 2009 Elsevier B.V. All rights reserved.