Injection-dependent lateral resistance in front-junction solar cells with nc-Si:H and a-Si:H hole selective contact

We investigate the role of lateral transport of minority carriers in the wafer for front-junction solar cells. The study is based on two silicon heterojunction solar cells with p-type amorphous (a-Si), and nanocrystalline (nc-Si) silicon as hole selective layer respectively. The solar cells feature similar certified efficiencies (23.23% and 23.45%). Unexpectedly, FF and RS at MPP of both solar cells are also similar. Fitting the JV curves in high-forward bias, and analytical calculations suggest that lateral transport is also taking place in the wafer at high injection, despite the front-junction configuration. This is supported by numerical device simulations. Both reveal that junction-related RS is lower with nc-Si(p) than with a-Si(p). The results underline the importance of analyzing JV curves over a wide voltage range to unravel different phenomena determining FF.