The preparation and characterization of NiTe 2 back contacts to CdTe/CdS cells are described. NiTe 2 is formed on p-CdTe by electroless deposition at low reductant concentrations, producing devices that are superior ͑conversion efficiencies often exceeding 10%͒ to those contacted with electroless Ni. X-ray photoelectron spectroscopy and X-ray diffraction showed the product to be nickel͑II͒ ditelluride (Ni 2ϩ Te 2 2Ϫ), produced, in the catalytic presence of Al 3ϩ ions, by the reaction of Ni 2ϩ ions with a Te-rich CdTe surface, which is formed by an in situ etch in the chemical bath. Preliminary results indicate that Ni, from NiTe 2 , is not mobile within the cell structure, which is expected to be favorable for stability. Cells exhibit degradation when exposed to H 2 O vapor. However, this effect was found to be reversible, with performance improving to near predegradation values following cell transfer to dry air conditions.

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Formation and Characterization of Electroless-Deposited NiTe 2 Back Contacts to CdTe/CdS Thin-Film Solar Cells. -NiTe 2 back contacts to CdTe/CdS solar cells are formed by electroless deposition on p-CdTe from aqueous alkaline chemical baths containing NiCl 2 ·6H 2 O and low concentrations (¡0.1 M) of NaH 2 PO 2 . The samples are characterized by XRD and XPS. NiTe 2 is produced in the catalytic presence of Al 3+ ions by the reaction of Ni 2+ ions with a Te-rich CdTe surface, formed by an in situ etch in the deposition bath. The produced devices exhibit reasonable photovoltaic performance, with conversion efficiencies of ¿10%. NiTe 2 contacts offer promising stability considerations, because Ni is shown to be not mobile in the cell structure. -(DOBSON, KEVIN D.; ROTLEVI, OFER; ROSE, DOUG; HODES, GARY; J.