Annealed Zn(1-x)Mg(x)O/CU(In,Ga)Sc(2) (CIGS) interfaces have been characterized by ultraviolet light excited time-resolved photoluminescence (TRPL). The TRPL lifetime of the Zn(1-x)Mg(x)O/CIGS film increased on increasing the annealing temperature to 250 degrees C, whereas the TRPL lifetime of the CdS/ClGS film had little change by annealing at temperatures lower than 200 degrees C. This is attributed to the recovery of physical damages by annealing, induced by sputtering of the Zn(1-x)Mg(x)O film. The TRPL lifetime abruptly decreased with annealing at 300 degrees C. The diffusion of excess Zn from the Zn(1-x)Mg(x)O film into the CIGS interface is clearly observed in secondary ion mass spectroscopy (SIMS) depth profiles. These results indicate that excess Zn at the vicinity of the CIGS surface acts as non-radiative centers at the interface. The TRPL lifetime of the Zn(1-x)Mg(x)O/CIGS film annealed at 250 degrees C reached values to be comparable to that of the as-deposited CdS/ClGS him. Performance of the Zn(1-x)Mg(x)O/CIGS cells varied with the annealing temperature in the same manner as the TRIII. lifetime. The highest efficiency of the Zn(1-x)Mg(x)O/CIGS solar cells was achieved for annealing at 250 degrees C. The results of the TRPL. lifetime on annealing show that the cell efficiency is strongly influenced by the Zn(1-x)Mg(x)O/CIGS interface states related to the clarnages and diffusion of Zn. (C) 2008 Elsevier B.V. All rights reserved.