Photoluminescence of CuInS2-based semiconductor quantum dots; Its origin and the effect of ZnS coating

Abstract

The origin of the size-dependent photoluminescence (PL) of CuInS2-ZnS alloyed quantum dots and the effect of a ZnS thin layer coating on PL properties were studied. The PL emission band shifted to the shorter wavelength region with a decrease in the crystal size. A time-resolved measurement indicated that the PL lifetime for the lower energy component of the emission band was longer than that of the higher energy component. Although this is a characteristic feature of the donor-acceptor pair (DAP) recombination, the size dependent shift of the band was too large to be attributed to DAP recombination. The emission was attributed to an electronic transition from the quantum confined conduction band to an acceptor level. By coating with a ZnS thin layer the PL quantum yield increased up to 31%. © 2009 IOP Publishing Ltd.