Designing a front contact ink for SiN/sub x/ coated polycrystalline Si solar cells

Enhancing the solar cell performance as measured by higher fill factor (FF) and higher energy conversion efficiency (/spl eta/) requires minimizing both series resistance (R/sub s/) and shadow losses, and maximizing shunt resistance (R/sub sh/). A typical front contact Ag ink contains metal powders, glasses, and oxides suspended in an organic media. The effect of ink variables such as metal powder packing, glass chemistry, glass-SiN/sub x/-Si interaction, and diffusion of trace elements into Si on the R/sub s/ and R/sub SH/ was studied using SEM, SIMS and resistances measurements. Based on this study, new ink formulations with low Rs and minimal diffusion of impurities into the junction were designed to obtain FF>77% and /spl eta/>15% on a polycrystalline Si solar cell.