R&D centre, imec has implemented a laser doping process to its i-PERC solar cell that pushes conversion efficiencies to 20.2%, while claiming lower processing costs that could result in faster commercial adoption.
According to imec, a laser doping processing sequence eliminates the need of a furnace firing step to realise the local aluminium Back Surface Field (BSF). Replacement of the high-temperature ste, avoids passivation degradation of the rear (Al2O3) layer created by atomic layer deposition (ALD).
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The replacement laser doping step is also said to avoid optical degradation of the rear dielectric/metal stack that generates higher conversion efficiencies. The new process sequence is said to be extremely simple as the thin ALD (Al2O3) acts at the same time as passivation layer and doping source, while laser processing enables in one step the contact patterning and the local BSF formation.
In addition, the high Fill Factor of the cells (up to 80%) indicates an excellent contact quality, according to imec.
Combined with imec’s Ni/Cu plating sequence for front contact formation, a low temperature metallisation solution for i-PERC cells has been developed.
“Cost-of-ownership and process simplicity are key factor for the industry to adopt new technologies,” said Jozef Szlufcik, Si PV programme director at imec. “Our achievement, implying a substantial simplification of the i-PERC manufacturing process, is an important step towards reducing the cost-of-ownership of i-PERC technology and as such, a milestone in bringing this high-efficiency technology for silicon solar cells to the market.”
imec achieved the 20.2% conversion efficiency using large area (156x156mm2) i-PERC silicon cells on p-type Cz-Si.
At last year's EU PVSEC, imec, RENA and SoLayTec presented a thin (165µm), large area (156x156mm2) i-PERC-type solar cells with ALD passivation that achieved a cell efficiency of 19.6%, without a selective emitter using an industrial screen printing process flow. At this year's event, the team demonstrated at 20.1% cell.
