Enhancing dielectric-silicon interfaces through surface electric fields during firing

The sample and measurement of excess carrier concentration

Hydrogen passivation from dielectrics plays a pivotal role in enhancing the performance of silicon solar cells.  

In this latest work* from Professor Sebastian Bonilla, Dr Isabel Al-Dhahir, Dr Xinya Niu and colleagues from Trina Solar and The University of New South Wales, the authors demonstrate how controlling carrier populations through charge-assisted field effect passivation can influence interface chemistry.  By inducing a corona electric field on the surface of a thin film stack they observed significant modifications to the silicon-dielectric interface upon annealing, which correlated with the characteristics of interface defects.  The passivation properties of the interfaces strongly depended on the polarity and strength of the electric field during firing, as well as the dielectric materials in the layer stack.

The authors show that the surface electric fields not only influenced surface carrier population but that they also affected the resulting chemical interface properties post-annealing.  They postulate that hydrogen migration played a role in these observed effects.

Leveraging the corona-induced electric field enabled fine-tuning of both the chemical and field-effect passivation in thin film surface dielectrics, resulting in recombination current densities as low as 2.8fAcm-2 in research-grade float zone silicon, and 14fAcm-2 in industrial-grade textured silicon.  

The simplicity and versatility of the thin film electric polarisation enabled a new strategy for controlling and exploiting the chemical enhancement of interfaces in solar cell devices, from current TOPCon and PERC devices to future multijunction silicon-based cells.  


*'Enhancing dielectric-silicon interfaces through surface electric fields during firing', published in Solar Energy Materials and Solar Cells.