Na incorporation in Mo and CuInSe2 from production processes

Results of characterization of thin films of Mo deposited by DC magnetron s puttering on soda-lime glass (Mo/SLG) and CuInSe2 (CIS) on Mo/SLG are prese nted. The primary objective of the work was to clarify the factors determin ing the concentration of Na in commercial-grade CIS. Mo films were deposite d by three laboratories manufacturing CIS thin film solar cells. Analysis w as by secondary ion mass spectrometry, scanning electron microscopy and X-r ay diffraction. Changes in Mo deposition parameters in general affected the Na level but there was no obvious link to any single Mo deposition paramet er. Oxygen content directly affected the Na level. The Na behavior was not obviously connected to film preferred orientation. Selenization of the Mo l ayers was also examined, Elemental Se vapor was found to produce significan tly less selenization than H2Se. The amount of selenization was also strong ly dependent upon Mo deposition conditions, although a specific source of t he change in reaction rate was not found. Na distributions in the CIS depos ited on the Mo were not limited by the diffusivity of the Na. The Na concen tration in the CIS was increased by annealing the Mo films both with and wi thout intentionally added Na. The Na level in the CIS appears to be set mor e by the CIS deposition process than by the Na concentration in the Mo so l ong as the Mo contains sufficient Na to saturate the available sites in the CIS. (C) 1999 Published by Elsevier Science B.V. All rights reserved.