Growth of Cu(In,Ga)Se-2 thin films by coevaporation using alkaline precursors

CIGS layers were grown using NaF and LiF precursor layers with different th icknesses deposited on top of the Mo back contact layer prior to the CIGS d eposition. The substrates were soda lime glass with and without Na diffusio n barriers. Two types of barriers were used, silica and alumina. The CIGS l ayers were analysed structurally with SEM, TEM and XRD, and solar cell devi ces were prepared. We found improvements in grain structure, film texture a nd surface flatness when NaF precursor layers were used as compared to Na-f ree and Na-poor samples. Also electrically we found that the solar cell eff iciency increased with modest additions of Na. Changes in film morphology s aturated at an NaF thickness of 30 Angstrom and the solar cell efficiency s aturated with an NaF precursor thickness of about 100 Angstrom. NaF precurs or layers were also used at lower deposition temperatures and we observed i mproved solar cell efficiencies using the NaF precursor layer, even at subs trate temperatures as low as 310 degrees C. (C) 2000 Published by Elsevier Science S.A. All rights reserved.