Moly-poly solar cell: Industrial application of metal-oxide passivating contacts with a starting efficiency of 18.1%

We present large-area “moly-poly” cells, with a front side MoOx/a-Si:H(i) passivating contact and a rear-side poly-Si/SiOx stack, and we have demonstrated that MoOx based c-Si solar cell technology can be scaled to industrial wafer size. Excellent surface passivation was achieved using MoOx and poly-Si, leading to implied Voc values above 700 mV, and a final cell Voc of 687 mV. However, some care needs to be taken to avoid parasitic optical losses in the infra-red (IR) spectral range due to free-carrier absorption (FCA). These losses were investigated by comparing poly-Si layers of different thicknesses, deposited by low-pressure or plasma-enhanced chemical vapor deposition (LPCVD or PECVD), at the rear side of moly-poly cells. We found that ultra-thin PECVD layers are most suitable for solar cell applications due to a very good trade-off between surface passivation and reduced FCA. Based on this result, a 18.1% efficient 9.2 × 9.2 cm2 moly-poly cell was made, which is the highest reported efficiency so f...