Structural Defects in thin Film Amorphous Silicon Films Deposited on Textured TCO Material

ABSTRACTA cross sectional TME study has been conducted into the structure and morphology of p- and i-type a-Si:H layers of device quality deposited on textured TCO on glass. The layer thickness over peaks is shown to be equivalent to that for flat regions, while defective regions are found in narrow valleys, initiating from the pit of the valleys. These regions may act as regions of excessive recombination and/or shunting regions, thus leading to a reduced Voc and fill factor in thin solar cells. A cosine relationship was found between the deposited thickness and the facet angles of the surface TCO crystals. It is concluded that for best performance of the deposited layer, the deposition has to be completely isotropie, and that the preferred surface morphology of textured TCO be sharp peaks with wider valleys.