Towards All Screen Printed Back-Contact Back-Junction Silicon Solar Cells

We report recent progress in the adoption of an optimized screen-printable boron dopant material, which enables the cost-competitive fabrication of novel n-type silicon solar cells such as "nPERT" and "IBC" cells. We manufactured first "IBC" devices with an early version of our dopant material, a co-diffusion approach and evaporated electrodes, achieving an efficiency of 20.9 % in 2016. Since then we optimized the dopant material and co-diffusion processes, as reported in this work. These optimizations now enable a long-term printing of the dopant material, suited for mass production, while maintaining crucial performance parameters. Moreover, we demonstrate a co-diffusion setup with POCl3, which does not require any additional dopant sources and can instead be adjusted with a wet chemical etch back. Combined with new commercially available electrode pastes, which have been evaluated with regard to simultaneous contacting of n- and p-type dopings, all screen printed n-type solar cells become a mass market possibility in the near future.