imec has announced that it has improved its large area n-type Passivated Emitter, Rear Totally diffused (PERT) crystalline Si solar cell on 6” commercially available n-type Cz-Si wafers. The solar cell now has a conversion efficiency of 22.02%, which is the highest efficiency achieved for this type of two-side-contacted solar cell on an industrial large area wafer size.
Compared to p-type silicon solar cells, n-type cells do not suffer from light induced degradation and feature a higher tolerance to common metal impurities.
Alongside a 22.02% conversion efficiency, the n-PERT solar cell features an open-circuit voltage of 684mV, a short-circuit current of 39.9mA/cm2, and 80.7% fill factor. Laser doping introduced a selective front surface field, which improved efficiency by boosting open circuit voltage and short circuit current.
The n-PERT silicon solar cell features Ni/Cu/Ag front contacts and rear local contacts. The former were applied using an industrial plating tool from Meco, while the latter were applied by laser ablation of the rear passivation stack and its subsequent metallisation. The rear passivation stack includes a thin (less than 10nm) Atomic-Layer-Deposited (ALD) Al2O3 layer, deposited with the spatial ALD technique InPassion Lab from SoLayTec. The diffused front surface field and rear emitter as well as the anti-reflective coating are applied in a Tempress batch-type furnace.
“Our developments, resulting in additional improvement of the conversion efficiency, further confirm the potential of n-type PERT cells for next-gen highly efficient silicon solar cells” said Filip Duerinckx, Manager, n-PERT technology platform, imec. “This new efficiency record has been achieved while simultaneously simplifying the process, relying only on simplified cleans and without any expensive forming gas anneal. We are committed to further increasing the efficiency of this cell concept and adding to the industrial value of the technology. This will enable bringing this technology to the market in short term.”