Abstract
The understanding of hydrogen and chemical interfaces in passivating contact stacks is critical for advancing high-efficiency silicon solar cells. This work employs time-of-flight elastic recoil detection analysis (ToF-ERDA) to profile elemental depth distributions, particularly the unambiguous characterisation of hydrogen, in key surface passivation dielectric nanolayers—SiNx, AlOx, and Al-doped ZnO (AZO). By leveraging the high mass resolution and low fluence of ToF-ERDA, combined with Monte Carlo simulations (MCERD), our work resolves hydrogen distributions and distinguishes overlapping signals from Si and Al, enabling precise analysis of interface composition. SiNx layers exhibit hydrogen contents up to 21 at.%, with redistribution and performance degradation observed after high-temperature annealing. In contrast, AlOx shows lower hydrogen content (∼2 at.%) but significant lifetime improvements post-annealing, indicating dominant field-effect passivation. For SiNx/AlOx double-layer stacks, enhanced hydrogen diffusion into AlOx was observed, suggesting SiNx as a hydrogen source. AZO/AlOx stacks demonstrated excellent passivation (iVOC > 730 mV) post-anneal, with hydrogen predominantly located in the AZO, challenging conventional views of AlOx as the main hydrogen source. These findings underline the value of ToF-ERDA for evaluating passivation mechanisms and demonstrate the tools versatility and usefulness in characterising dielectric nanolayers.
[Display omitted]
•ToF-ERDA accurately depth profiles hydrogen in solar cell passivation layers.•An onset for rapid effusion of hydrogen in SiNx layers occurs at >600C, linked to reductions in surface passivation.•AlOx layers gain hydrogen from SiNx, showing effectiveness as a H diffusion source.•AZO/AlOx stacks show excellent passivation, potentially with AZO as primary H source.•MCERD simulations refine depth profiles and deconvolute overlapping Si and Al.