3.4.3 Silicon-Passivated Contact Bottom Cell

• Progress research on monolithic bottom silicon devices based on polysilicon and PERC contact structures toward demonstration of the completed tandem devices.

• Advance both front and rear surface technologies, targeting improved optical and electrical performances, including (i) the development of sub-micron pyramid texturing on the front surface, to reduce front reflection losses and long wavelength light trapping enhancements and (ii) further development of polysilicon-based recombination frontjunctions for thermally stability and compatibility with subsequent top cell fabrication processes. On the rear surface, research will focus towards incorporating rear texturing and a compatible, doped polysilicon contact layer, in combination with enhancement to rear optical properties by inclusion of optimised dielectric (such as SiNx).

• Progress in patterning technologies for contact opening on doped polysilicon layers to enable optimised contact opening through the rear dielectric layers.

• Progress the development of all-polysilicon based tunnel-junction, addressing reliability and stability issues of metal-oxide based carrier-transport inter-layers.