Firing stable surface passivation using all-PECVD stacks of SiOx:H and SiNx:H

Surface passivation stack systems, all deposited using PECVD, are investigated. Stacks of SiOx, SiNx and SiOx (PECVD-ONO, patent pending) are shown to be a suitable passivation layer system for the rear of silicon solar cells (p type bulk). The thermal stability during annealing at 425 °C and firing of screen printed front contacts could be shown with surface recombination velocities below 60 cm/s after firing. Solar cell precursors without metallisation showing implied Voc values above 680 mV are presented. Hydrogen depth profiling using nuclear reaction analysis (NRA) shows the hydrogen distribution after deposition and different thermal treatments. Finally, solar cells using the new stack system as rear passivation and laser-fired rear contacts are presented with a peak efficiency of 19.4 %. IQE measurements show PECVD-ONO to be clearly superior to Al-BSF