Time-resolved photoluminescence properties of CuInS2/ZnS nanocrystals: Influence of intrinsic defects and external impurities

Photoluminescence (PL) lifetime studies of CuInS2 nanocrystals (NCs) are carried out after synthesizing core-shell and compositionally variant structures using time-resolved PL spectroscopy. Long-lived excited state decay times are observed for the NCs, and decay times are very much dependent on the size of the CuInS2 NCs. The emission bands are attributed to the surface (shorter PL lifetime) and defect (longer PL lifetime) related trap states, respectively. The decay dynamics of the CuInS2 NC’s excited-state carriers is very sensitive to the surface, intrinsic defects, and extrinsic impurities. The observed large Stokes shifts and broad PL spectra also reveal the involvement of the defect-related trapping sites in the emission process.