Study of Recombination in Cu(In,Ga)Se2 Solar Cells by Time-Resolved Photoluminescence

Abstract

AbstractTime-resolved PL (TR-PL) measurements have been carried out on Cu(In1-x,Gax)Se2 (CIGS) thin films and solar cells to study the recombination of photo-generated minority carriers . Room temperature PL of both CIGS thin films and solar cells exhibited band-to-band transition for alloy composition x of 0-0.4, and PL decay curves have been utilized as a measure of carrier lifetime. The solar cell fabrication leads to the enhancement of band-to-band PL intensity, reduction of defect-related PL, and increase of PL decay time. It is noted that the increase in PL decay time has been observed in CIGS films after CBD-CdS deposition. Solar cells with high conversion efficiency are characterized by both high PL intensity and long PL decay time. The PL decay curve of CIGS solar cell is studied in terms of the alloy composition x. For small x, PL decay times of CIGS solar cells are almost independent of the emission photon energy. For large x, PL decay time depended on PL emission energy. he result suggests the change of the recombination mechanism in the CIGS solar cells with the change in the alloy composition x.