Time-resolved photoluminescence in Cu(In,Ga)Se2 thin films and solar cells

Room temperature time-resolved photoluminescence JR-PL) measurements have been performed on Cu(ln,Ga)Se, (CIGS) thin films and solar cells to clarify the recombination process of the photo-generated minority carrier. Both films and solar cells exhibited PL decay curves composed of the dominant fast (0.7-2 ns) and weak slow (3-10 ns) exponential decay curves. PL lifetime of the cell is longer than that of the thin films, indicating the longer minority carrier lifetime for the hetero-structures than in thin films. The increase of PL lifetime is consistent with the enhancement of the PL intensity and the elimination of defect-related Pt, as a result of the solar cell formation. These results are discussed in terms of the recombination process of carriers in films and hetero-structures. The relationship between the PL lifetime of the CIGS solar cells and the cell conversion efficiency is described. (C) 2006 Elsevier B.V. All rights reserved.