Recombination in n-i-p (substrate) a-Si:H solar cells with silicon carbide and protocrystalline p-layers

A study was carried out on hydrogenated amorphous silicon (a-Si:H) n-i-p (substrate) solar cell structures with p-a-SiC:H and highly diluted p-Si:H layers grown with different dilution ratios R=[H-2]/[SiH4]. The contributions of the recombination at the p/i interfaces to the forward bias dark current characteristics were identified and quantified for the different cell structures. In both cell structures the role of the p/i interfaces was identified and it is found that the lowest p/i interface recombination is obtained with protocrystalline p-Si:H layers having no microcrystalline component. The results with p-Si:H layers are attributed not only to their properties but also to the subsurface modification of the intrinsic layer. Evidence is also presented that points to the beneficial effects of the high hydrogen dilution and power used in the deposition of these p-layers in creating the p/i interface regions. The limitations on 1 sun open circuit voltage (V-OC) imposed by the p/i recombination present in all the cell structures is consistent with the mechanisms proposed by Deng et al.[1]. The results presented here also point to why the 1 sun V-OC in protocrystal line p-Si:H solar cells is higher than that in p-a-SiC:H cells.