Effects of Gas Flow Ratio on Optical Properties of PECVD Grown Single Layer Anti-reflecting Coating for Silicon Solar Cells

Design of SiNx / SiOx single layer antireflection coating has been developed which tunes both the layer thickness and the deposition gas flow ratio. The method is built up for achieving maximum available carrier generation rate. The carrier generation rate estimation is based on internal and external quantum efficiency calculations. In this report the effect of optical reflection and absorption on external efficiency is widely studied. The model is based on wideband photonic parameters of silicon nitride / oxide which are deposited with PECVD machine under different deposition criteria. Effect of gas flow ratio on the dielectric refractive index and extinction factor are investigated by wideband photonic measurements. For silicon nitride anti reflection coating, the optimized coating consists of 63nm SiNx layer with Silane to Ammonia gas ratio of 4. The estimated carrier generation rate is 1.88×1017 cm-2s-1. The best possible results for silicon oxide has been derived with 88.9nm SiOx with Silane to Nitrous Oxide gas ratio of 1; In this case the carrier generation rate will be 1.83×1017 cm-2s-1. The proposed anti reflection coatings are deposited on single crystal silicon substrate, the measured optical reflection coefficients are in very good agreement with the developed theory.

Keywords:

Anti reflection coating , solar cells , PECVD , optical index