Electrical properties of Cu–In–S absorber prepared on Cu tape (CISCuT)

An In precursor on a Cu tape, sulfurized under special transient conditions, shows an internal structure with at least four different semiconducting layers. This structure has a rectifying I– V characteristic also without any buffer layer. The space-charge region is located near the top surface in the upper part of the In-rich layer having a columnar structure, and in the top layer. Deeper-lying layers provide a good contact to the In-rich layer, but show no carrier collection themselves. An EBIC investigation and an original thermopower measurement revealed a pnp-structure with the n-type layer being the In-rich one. The lower part of the film contains a short-circuited p–n junction, switched in series in the opposite direction. One proposal for the band structure of the absorber is presented.