When Na was present in small quantities, it formed defects on Cu and In sites. The Na on Cu sites did not create levels in the band gap, while Na on In sites created acceptor levels that were shallower than CuIn. The major effect of Na was to eliminate InCu defects. The quenching of both InCu and VCu by Na reduced the stability of the (2VCu-+InCu2+); thus suppressing the formation of so-called ordered defect compounds. It was known that Na on the surface catalyzed the dissociation of O2 into atomic O that substituted for Se vacancies and converted them into OSe. It was found here, however, that OSe was a deep acceptor rather than a shallow acceptor.

Effects of Na on the electrical and structural properties of CuInSe2 S.H.Wei, S.B.Zhang, A.Zunger: Journal of Applied Physics, 1999, 85[10], 7214-8