Firing-stable PassDop passivation for screen printed n-type PERL solar cells based on a-SiNx:P

Rear side passivation and local back surface field formation are two of the main technological challenges for n-type PERL silicon solar cells. A promising approach is the PassDop process. This process combines a phosphorous doped passivation layer deposited on the rear side with a subsequent laser process to create both a local contact opening as well as a local back surface field. In this paper we introduce a new layer system based on doped amorphous silicon nitride (the fPassDop process) which is able to passivate the n-type surface after a firing step as typically used for screen printed contacts. After the firing step, an effective recombination velocity <5 cm/s can be reached with this layer. The measured sheet resistance is in the range of 60 Ω/sq after the laser process. In a first test the fPassDop process is applied to small area solar cells achieving a conversion efficiency of 21.3% (675 mV Voc). Additionally, we fabricated large area n-type solar cells with screen printed front side contacts achieving 20.1% efficiency and Voc of 668 mV.