Aluminum-doped zinc oxide (ZnO:Al) [AZO] is a good candidate to be used as a transparent conducting oxide [TCO]. For solar cells having a hydrogenated amorphous silicon carbide [a-SiC:H] or hydrogenated amorphous silicon [a-Si:H] window layer, the use of the AZO as TCO results in a deterioration of fill factor [FF], so fluorine-doped tin oxide (Sn02:F) [FTO] is usually preferred as a TCO. In this study, interface engineering is carried out at the AZO and p-type a-SiC:H interface to obtain a better solar cell performance without loss in the FF. The abrupt potential barrier at the interface of AZO and p-type a-SiC:H is made gradual by inserting a buffer layer. A few-nanometer-thick nanocrystalline silicon buffer layer between the AZO and a-SiC:H enhances the FF from 67% to 73% and the efficiency from 7.30% to 8.18%. Further improvements in the solar cell performance are expected through optimization of cell structures and doping levels.

P-layer of a p-i-n type amorphous silicon solar cell helps in creating a built-in electric field inside the cell; it also contributes to parasitic absorption loss of incident light. Here, we report optimization of these two characteristic contributions of the p-layer of the cell. We used a highly transparent p-type hydrogenated amorphous silicon carbide (p-a-Si 1−x C x ∶H) window layer in an amorphous silicon solar cell. With the increased transparency of the p-type layer, the solar cell showed an improvement in short-circuit current density by 17%, along with improvement in blue response of its external quantum efficiency, although further thinner player showed lower open-circuit voltage. Such a cell shows low light-induced degradation and a promise to be used in high-efficiency multijunction solar cell.

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Ttis paper briefly introduces silicon based thin film solar cells: amorphous (a-Si:H). microcrystalline (pc-Si:H) single junction and a-Si:H/pc-Si:H tandem solar cells. The major difference of a-Si:H and pGSi:H cells comes from electro-optical properties of intrinsic Si-films (active layer) that absorb incident photon and generate electron-hole pairs. The a-Si:H film has energy band-gap (Eg) of 1.7-1.8eV and solar cells incorporating this wide Eg a-Si:H material as active layer commonly give high voltage and low current, when illuminated, compared to pc-Si:H solar cells that employ low Eg (l.leV) material. This Eg difference of two materials make possible tandem configuration in order to effectively use incident photon energy. The a-Si:H/paSi:H tandem solar cells, therefore, have a great potential for low cost photovoltaic device by its various advantages such as low material cost by thinfilm structure on low cost substrate instead of expensive c-Si wafer and high conversion efficiency by tandem structure. In this paper, the structure, process and operation properties of Si-based thin-film solar cells will be discussed.

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