Nanoelectronics research centre Imec has announced that they have developed a 156mm x 156mm i-PERC-type silicon solar cell using a new processing sequence, based on laser doping from a thin atomic layer deposited (ALD) aluminium oxide (Al2O3) layer, to realise the local aluminium Back Surface Field (BSF) and Ni/Cu plating to form the front contact. The cells achieved average conversion efficiencies of 20.2 per cent.
The laser doping processing sequence eliminates the necessity of a firing step to create the local BSF in i-PERC cells. Combined with Imec’s Ni/Cu plating sequence for front contact formation, it provides a low temperature metallisation solution for i-PERC cells. By avoiding high temperature conditions, passivation degradation of the rear Al2O3 layer and optical degradation of the rear dielectric/metal stack are prevented.
Because the thin ALD Al2O3 acts at the same time as passivation layer and doping source and laser processing enables the contact patterning and the local BSF formation in one step, simplifying the process.
The complete solar cell process was executed at Imec and the resulting i-PERC cells on p-type Cz-Si achieved an average conversion efficiency of 20.2 per cent. Even though only low temperature anneal was used, the high Fill Factor of the cells is of up to 80 per cent, which indicates good contact quality.
‘Cost-of-ownership and process simplicity are key factors for the industry to adopt new technologies,' stated Jozef Szlufcik, Si PV program 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.’