This study addresses the role of p-type buffer layers between ZnO:AI (AZO) TCO and p a-SiC:H window layer. When AZO is used as a front TCO in conventional a-Si:H solar cells incorporating p a-SiC:H window, the fill factor (FF) significantly decreases in different with SnO 2:F (FTO). Various buffer layers with different conductivity and crystalline properties are inserted between AZO and p aSiC: H and solar cell performances are compared. The FF deterioration of AZO/p a-SiC:H cells is directly related to the interface potential barrier. This potential barrier can be controlled by tuning electron affinity and mobility gap as well as electrical conductivity of buffer layers. The p a-Si:H buffer improves FF up to 0.72, which results from high conductivity of buffer layer. The p a-Si:H buffers also improves FF although they have similarly low conductivity with p a-SiC:H because of low electron affinity and/or mobility gap.