Microstructural Characterization and Mathematical Model of Microcolloids Contact Mechanism in c-Si Solar Cells

摘要

The current paths in the screen-printed contact of a solar cell have been proposed to be (i) through Ag crystallites embedded in Si, (ii) tunneling through the thin interface glass layer between silicon and gridline and (iii) through Ag nanoparticle assisted tunneling. The fourth path through the micro-colloids is hereby proposed based on the characterization and mathematical model of a screen-printed contact to a 95 Ω/sq emitter. According to Raman spectroscopy and conductive AFM, it has been established that the glass with micro-colloids after contact formation is highly conductive due to colloids containing low bandgap semi-metals. Thus, such glass serves as a path with low contact resistance for current transport from Si to the Ag gridline. This model is particularly applicable to lowly doped emitter, which would not be contacted ordinarily with low contact resistance based on the barrier height of the interface dielectric.