S. Nishiwaki et al., Preparation of Cu(In,Ga)Se-2 thin films from In-Ga-Se precursors for high-efficiency solar cells, J MATER RES, 14(12), 1999, pp. 4514-4520
Growth of Cu(In,Ga)Se-2 (CIGS) films from In-Ga-Se precursors was character
ized by scanning Auger electron spectroscopy (SAES), secondary ion mass spe
ctroscopy (SIMS), x-ray diffraction, scanning electron microscopy, and tran
smission electron microscopy (TEM). In-Ga-Se precursor layers were deposite
d on Mo-coated soda-lime glass, and then the layers were exposed to Cu and
Se fluxes to form CIGS films. The SIMS and SAES analyses showed a homogeneo
us distribution of Cu throughout the CIGS films during the deposition of Cu
and Se. The phase changes observed in the CIGS films during the deposition
of Cu and Se on the In-Ga-Se precursor films were as follows: (In,Ga)(2)Se
-3 --> [Cu(In,Ga)(5)Se-8] --> Cu(In,Ga)(3)Se-5 --> Cu(In,Ga)Se-2. The grain
size increased from the submicron grains of the (In,Ga)(2)Se-3 precursor f
ilm to several micrometers in the stoichiometric Cu(In,Ga)Se-2 film. A grow
th model of CIGS crystals is introduced on the basis of the results of TEM
observations. CIGS crystals are mainly grown under (In,Ga)-rich conditions
in the preparation from In-Ga-Se precursor films.