Interface Engineering for Liquid-Phase Crystallized-Silicon Solar Cells on Glass

Liquid-phase crystallization (LPC) of silicon is a suitable method to grow large grained poly-crystalline silicon with wafer equivalent electronic quality on cheap glass substrates. Dielectric layers between glass and silicon (called interlayer) are not only crucial for the solar cell performance, but, they also provide wetting of the silicon during crystallization. So far, LPC-Si samples based on interlayers grown with plasma-enhanced chemical vapor deposition (PECVD) were annealed prior to crystallization to remove hydrogen in order to prevent delamination during crystallization. However, this step increases manufacturing time and disables integrated processing without extended vacuum breaks. In this work, PECVD-grown stacks with silicon oxide and silicon nitride, that is, SiOx/SiNx/SiOx (O/N/O), were developed aiming a high cell performance and a successful crystallization without prior annealing step. We found that the SiNx layer significantly influences adhesion and that an O/N/O stack with a nitrogen-rich SiNx layer in which hydrogen is only bonded to nitrogen, that is, no Si-H bonds, provides wetting without annealing step. The total amount of bonded hydrogen in the SiNx film was not crucial. Finally, based on the presented O/N/O stack, LPC-Si solar cells with almost 630mV open circuit voltage and a conversion efficiency of up to 13.2% were obtained.