TLM measurements varying the intrinsic a-Si:H layer thickness in silicon heterojunction solar cells

Silicon heterojunction solar cells are a promising device architecture due to their high efficiencies, yet these cells tend to suffer from high series resistances. Until recently, little has been done to understand the main factors contributing to the high resistance. Here we begin a systematic analysis to determine the important interactions between the different layers in the hole-collecting contact consisting of a stack of a-Si:H(i)/aSi:H(p)/ITO/Ag. We attempt to address how the stack performs when the intrinsic amorphous silicon (a-Si:H(i)) layer thickness is varied. Specifically, we determine how the thickness affects the fill factor of the cell and assess how much of the detriment is due to the contact resistivity. For increasing a-Si:H(i) thicknesses between 4 and 16 nm, we find contact resistivities increasing from 0.48 to 1.9 Ωcm
²
and fill factors decreasing from 76.9% to 71.1%. Additionally, to understand the physics behind these effects, we simulate the contact resistivity variation by modeling the ITO as a Schottky contact and a semiconductor.