A. Rockett et al., Na in selenized Cu(In,Ga)Se-2 on Na-containing and Na-free glasses: distribution, grain structure, and device performances, THIN SOL FI, 372(1-2), 2000, pp. 212-217
We examined the effect of deposition of Na on Mo-coated glasses and the Na
content of the substrate glass on standard production Cu(In1-xGax)Se-2 (CIG
S)-based solar cells fabricated by selenization of Cu-Ga-In precursor thin
films. Under optimal conditions, net Na content has a larger effect on the
films than does the choice of substrate glass. Device performances improved
with modest amounts of added Na on borosilicate glass. Device performances
on soda-lime glass were not improved by adding Na. The supply of Na appear
s to have been adequate from the glass itself. A peak in device performance
was found as a function of integrated Na in the CIGS layer as determined b
y secondary ion mass spectrometry (SIMS). The Na is found primarily in the
areas of decreased grain size in the selenized CIGS where Ga is also found.
S, deposited with the Na does not end up in the same place as does the Na.
Rather, it tends to move toward the surface and accumulate in a buried lay
er. This is probably due to the reaction process rather than to the microst
ructure. Oxygen has no apparent effect on Na behavior in the CIGS. (C) 2000
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