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The Australian National University

Back Contact Cells

ANU is developing high-efficiency interdigitated back-contact (IBC) n-type silicon solar cells. Compared to standard front surface emitter solar cells, IBC cells offers many advantages such as no metal shading on front surface; a higher metal coverage leading to lower resistive losses (since there is no trade-off between metal coverage and shading); better surface passivation of sunward surface (since the front surface is not contacted and since lateral transfer of current to metal fingers is less important); improved rear optics and light trapping; and simpler cell-interconnecting system. Besides, adoption of n-type Si in IBC cell design is advantageous since carrier lifetime of n-type Si is less susceptible to reduction from metal and oxygen impurities.

Diagram of a back contect cell

Since the development of IBC cells started in April 2011, encouraging cell efficiencies – 19% (16-cm2), 21% (16-cm2) and 22% (13-cm2) – have been achieved. The fabrication of these highly efficient cells is based on the less-complicated process sequence. The development work is progressing steadily to not only increase the efficiency, but also set the record cell efficiency (>25%) for the rear-contact solar cells.

Chart showing milli-amps per cm squared, which starts at minus 40 milli-amps per cm squared for 0 volts, and starts increasing to 0 milli-amps per cm squared once voltage is greater than 0.55 volts.


  1. N. Zin, A. Blakers, et al., "Laser-assisted Shunt Removal on High Efficiency Silicon Solar Cells," submitted for publication at the 27th EUPVSEC, Hamburg, Germany, September 2012.
  2. N. Zin, A. Blakers, et al., "Progress in the development of All-Back-Contacted Silicon Solar Cells," PV Asia Pacific Conference 2011, Singapore, 2011.
  3. N. Zin, A. Blakers, et al., "19% Efficient N-Type All-Back-Contact Silicon Wafer Solar Cells With Planar Front Surface," Australian and New Zealand Solar Energy Society Sydney, Australia, 2011.


  • Dr Ngwe Zin
  • Professor Andrew Blakers

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