High-Efficiency Full Back Contacted Cells Using Industrial Processes

Full-size (156 ×156 mm
²
) interdigitated back contact (IBC) solar cells have been developed with conventional industry processes. With PC1D simulation and short-flow experiment verification, we found that the tunnel junction shunting of rear n
⁺
/p
⁺
could be mitigated significantly by controlling the boron surface concentration; therefore, it is not necessary to form a gap between rear emitter and back surface field. Made by a novel yet relative simple process, the IBC cells preliminarily achieved 19.65% best efficiency with J
_sc
and V
_oc
as high as 40.5 mA/cm
²
and 655 mV, respectively, while FF was only 73.9% due to the low pseudo fill factor (Pff) and high series resistance. Through the optimization of the rear pattern process, Pff was improved up to 82.5% and FF up to 77%. With further optimization of emitter, front surface field, passivation, and rear pattern design, the cells potentially can achieve up to 22.0% efficiency in the near future.