European R&D facility, imec has achieved new solar cell record efficiency for its N-type, monocrystalline n-PERT (passivated emitter, rear totally diffused) process using commercial sized wafers and processing equipment. 

Imec said that a conversion efficiency of 22.02% was achieved and was calibrated at ISE CalLab and features an open-circuit voltage (Voc) of 684mV, a short-circuit current (Jsc) of 39.9 mA/cm2, and 80.7% fill factor (FF). 

“Our new developments, resulting in additional improvement of the conversion efficiency, further confirm the potential of n-type PERT cells for next-generation highly efficient silicon solar cells” said Filip Duerinckx, manager of imec’s n-PERT technology platform. “This new efficiency record has been achieved while simultaneously simplifying the process, relying only on simplified cleans and without any expensive Forming Gas Anneal (FGA). 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.”

Reiterating n-PERT’s commercial credentials, imec highlighted that the record efficiencies were obtained by incorporating a selective front surface field through laser doping, which generated improved open circuit voltage and short circuit current.

Imec’s n-PERT solar cells feature Ni/Cu/Ag front contacts, applied using an industrial plating tool from Meco, and rear local contacts obtained by laser ablation of the rear passivation stack and subsequent metallization. 

The rear passivation stack includes a thin (<10 nm) ALD deposited Al2O3 layer, using SoLayTec’s InPassion Lab tool.

The diffused Front Surface Field (FSF) and rear emitter as well as the Anti-Reflective Coating (ARC) are applied in a Tempress batch-type furnace. 

More gains in conversion efficiency are highly likely as the current n-PERT process does not include commercially available boron and phosphorous doping processes using ion implantation that could deliver close to 1% absolute efficiency gains.