Investigation of surface passivation schemes for p-type monocrystalline silicon solar cell

Abstract

This paper represents an experiment to analyze the dark saturation current densities of passivated surfaces for monocrystalline silicon solar cells. The samples are diffused at peak temperatures of 800–950 °C. Basically, symmetrical lifetime samples with different doping profiles are prepared with alkaline textured and saw damage etched (planar) surfaces. After POCl3 diffusion, the phosphorous silicate glass layers are removed in a wet chemical etching step. Several designs are chosen for the determination of the sheet resistance (Rsh), the concentration profile for excess charge carrier and the minority carrier effective lifetime of the diffused surfaces. The dark saturation current densities (Jo) and the doping profiles are determined accordingly via quasi-steady state photoconductance decay measurement and electrochemical capacitance–voltage measurement. Three different passivation schemes are investigated as follows: silicon nitride (SiNx) deposited by plasma-enhanced chemical vapor deposition (PECVD) technique, silicon-rich oxynitride (SiriOxNy) capped with a PECVD SiNx layer, and thin thermally grown oxide, capped with a PECVD SiNx layer.